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by Lt Cdr Geoffrey B Mason RN (Rtd) (c) 2005


HMS JASON (N 99) - Halcyon-class Minesweeper


Edited by Gordon Smith, Naval-History.Net

HMS Speedwell, sister ship (Navy Photos/Mark Teadham, click to enlarge)

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HALCYON-Class Minesweeper ordered from Ailsa SB  at Troon on 4th September 1936 with sister ship to be named HMS FRANKLIN as part of the 3rd Group of this Class. Her turbine propulsion machinery was to be supplied John I Thornycroft, Woolston. The ship was laid down on 12th December 1936 and launched on 6th October 1937 as the 16th RN warship to carry this name which had been introduced for a Fireship purchased in 1673. The name is taken from Greek mythology and was last used for an Armed Yacht hired in 1915. Build of this ship was completed for use as a Survey Ship on 9th June 1938.but in November that she was taken out of service and converted for use as a Fleet Minesweeper by HM Dockyard Portsmouth. She was re-commissioned for deployment as a convoy escort on 27th September 1939..After a successful WARSHIP WEEK National Savings campaign in December 1941 this ship was adopted by the civil community of St Austell, Cornwall.


B a t t l e   H o n o u r s


ATLANTIC 1940 - NORTH SEA 1941-42 -  ARCTIC 1943 - NORMANDY 1944


H e r a l d i c   D a t a

On a field Red, a golden fleece.


M a n n i n g   D i v i s i o n




D e t a i l s   o f   W a r   S e r v i c e


(for more ship information, go to Naval History Homepage and type name in Site Search



1 9 3 9


September             Dockyard work completed

                28th        Commissioned at Portsmouth for service in 1st Anti-submarine Striking Force.


October                  Completed Acceptance Trials and carried out minesweeping work-up

                12th        Sustained minor damage after grounding on Row Point.


November              Deployed for convoy defence in Home waters with Force




1 9 4 0


January                  Transferred to 3rd Anti-submarine Striking Force for service in Western Approaches Command.

to                            Deployed for convoy defence

July                         Pennant Number for visual signal purposes changed to J99 as part of changes made to all those

                                used by RN warships after May 1940.



                3rd          Under repair at Belfast.

                21st         On completion of trials and shipyard work resumed Convoy defence in NW Approaches.

                28th        Deployed with HM Corvette HIBISCUS for escort of mercantile convoy during passage from

                                Clyde to Methil.

                                (Note: These 19 ships had detached from inward convoy HX66 for passage to east coast ports.)

                30th        Under attack by U32 and U28 during which four mercantiles were sunk.


September             Convoy defence in continuation

                16th        Sustained significant structural damage to stem in collision with rescue tug SCHELDT.

                20th        Taken in hand for repair at HM Dockyard Rosyth.

                23rd        Resumed operational service on completion of dockyard work.

                                Deployed with Rosyth Escort Force for defence of convoys to and from Clyde.


October                  Rosyth Force convoy escort in continuation

                18th        Deployed as part of escort for inward Convoy HX79 to Liverpool during concentrated

                                U-Boat attacks during which 10 ships were sunk

                                For details see HITLER’S U-BOAT WAR by C Blair.

                                (Note: Inward Convoy SC7 was also under attack at this time.

                                The enemy attacks involving at least eight submarines were one of the heaviest

                                made in 1940 )


November              Rosyth deployment in continuation.




1 9 4 1


January                  Deployment with Rosyth Escort Force for convoy defence





                21st         Taken in hand for refit at Leith.



                26th        Resumed operational deployment at Rosyth on completion of dockyard work and


September             Convoy defence based at Rosyth in continuation




1 9 4 2


January                  Rosyth deployment in continuation



                25th        Under repair by HM Dockyard Rosyth

                28th        Resumed convoy defence duties at Rosyth


March                    Convoy defence based at Rosyth in continuation.

to                            Nominated for conversion for Fleet minesweeping duty including “Arcticisation”.



August                  Released from Rosyth Escort Force

                24th        Taken in hand for conversion and refit by HM Dockyard Rosyth.


September             Conversion and refit.





                24th        During trials on completion of refit work retained in dockyard for repairs

                26th        Under repair


1 9 4 3



                5th          Carried out sea trials on completion of repair.

                                On completion of trials deployed for minesweeping trials and shakedown prior

                                to detached service in North Russia.



                15th        Joined Convoy JW53 with HM Fleet Minesweeper HALCYON, HM Corvettes

                                BERGAMOT, POPPY and a Trawler. at Loch Ewe

                                part of escort during passage to Kola Inlet

                                (Note: This convoy experienced extreme weather during passage and many mercantiles

                                had to return due to weather damage or defects.

                                HMS HALCYON detached and took passage to Iceland on 22nd.)

                19th        Ocean escort of Fleet destroyers joined JW53.

                20th        HM Corvettes BLUEBELL and CAMELLIA joined JW53

                26th        Eastern Local Escort comprising HM Fleet Minesweeper BRITOMART and five Soviet

                                destroyers joined .

                27th        Detached from JW53 on arrival and joined HM Fleet Minesweepers BRITOMART,

                                HALCYON, HAZARD, GOSSAMER and SHARPSHOOTER for minesweeping, patrol

                                and convoy defence in North Russia.

                                For details of all warships and mercantiles involved in convoys to and from North Russia

                                see CONVOYS TO RUSSIA by RA Ruegg, THE RUSSIAN CONVOYS by B Schoefield,

                                CONVOY! by P Kemp and THE RUSSIA CONVOYS by R Woodman

                                (Note: JW53 was last Russian convoy in the 1943 season).


March                    North Russia deployment in continuation





                17th        Deployed with HM Fleet Minesweeper BRITOMART as escort during passage of Russian

                                icebreakers during passage from White Sea to Kara Sea.

                22nd       Detached with HMS BRITOMART from icebreakers on arrival in Kara Sea and returned to

                                Kola Inlet


July                         North Russia deployment in continuation.

to                            (Note: During service in North Russia these ships were frequently under air attack

October                  during patrol and minesweeping . In one attack HMS BRITOMART was

                                hit by two bombs which skidded along the upper deck and fell overboard

                                without detonating.

                                Service on board and during limited shore leave was far below standards

                                found during service in Home waters.

                                Nominated for return to UK



                1st           Joined Convoy RA54 with HMS BRITOMART in Kola Inlet for escort during passage to

                                Loch Ewe.

                                (Note: Other escort for return passage included Home Fleet destroyers and a corvette..

                                See references.)

                14th        Detached from RA54A on arrival in Home waters.

                                Passage to Portsmouth

                22nd       Taken in hand for refit by HM Dockyard.


December              Under refit


1 9 4 4


January                  Under refit.


February                Carried out harbour and sea trials.

                                Resumed service with 1st Flotilla.

                                Passage from Portsmouth to join ships of 15th Minesweeping Flotilla in Cromarty

                                Firth for night minesweeping exercises.

                28th        Took passage from Cromarty Firth on completion and sailed for Scapa Flow.


March                    Carried out anti-submarine exercises based at Scapa Flow with HMS HARRIER, HMS

                                HUSSAR and HMS SPEEDWELL.

                                Nominated with ships of Flotilla for minesweeping support during planned

                                allied landings in Normandy (Operation NEPTUNE).

                9th          On completion of anti-submarine exercises carried out minesweeping exercises with other

                                ships of 1st Flotilla.



                4th          Under repair by HM Dockyard Rosyth.

                10th        On completion rejoined Flotilla.

                                Passage to Portsmouth from Scapa Flow with Flotilla and called at North Shields and Harwich.

                                Joined Force S with ships of Flotilla.


May                        Nominated with Flotilla for mine clearance of approach Channels to the beach head anchorage


                                (Note: Two minesweeping Motor Launches, one Isles-Class Trawler and three trawlers

                                were attached to Flotilla for danlaying during this specialised operation

                                Took part in preparatory exercises with ships of Force S.

                                (Exercise FABIUS)

                                Carried out night sweeping exercises with Flotilla.

                                For details of naval activities before and during landings see LANDINGS IN

                                NORMANDY JUNE 1944 (HMSO), OPERATION NEPTUNE by K Edwards

.                               and D-DAY SHIPS by J de Winser.


June                        Deployed at Portsmouth for briefing and preparations for minesweeping of Channel 9 in

                                advance of Assault convoys.

                4th          Operation delayed by 24 hours.

                5th          Sailed from Solent to commence Channel 9 clearance.

                                No mines cleared or exploded.

                6th          On completion deployed for mine sweeping of anchorages.

                8th          Deployed for widening approach Channels and defence patrols off Eastern Task Force landing

                to            areas.

                17th        Carried out Channel convoy escort as required.

                18th        Involved in collision and sustained significant damage and flooding in forward structure.

                                Released from Force s and took passage to Portsmouth.

                20th        Deployed at Portsmouth to await repair


July                         Under repair



                14th        Carried out trials after repair and resumed Flotilla service.

                                Deployed for minesweeping off Normandy for minesweeping and patrol off Arromanches

                                with HM Minesweepers HARRIER, HUSSAR, BRITOMART , GLEANER and


                22nd       Transferred to Le Havre area for mine sweeping operation in anchorage

                                Selected for bombardment of enemy positions by HM Battleship WARSPITE,

                                HM Monitors EREBUS and ROBERTS.

                23rd        Under shore fire during minesweeping operations.

                26th        Permission to remain in area instead of taking passage back to Arromanches

                                approved in order to complete clearance.

                27th        Deployed as Senior Officer’s ship during final clearance, came under rocket attacks by

                                RAF TYPHOON aircraft. Sustained major damage.

                                (Note: HMS BRITOMART and HMS HUSSAR were sunk, HMS SALAMANDER

                                damaged beyond economic repair and two trawlers damaged..

                                For details see OUT SWEEPS by Lund and Ludlam, FRIEND OR FOE by P Kemp

                                and Naval Staff History.

                                This disaster was directly due to failure of Flag Officer British Assault Area to ensure

                                that approval of extended minesweeping operation had been advised to all concerned

                                with air operations.)

                                Passage to Portsmouth


September             Deployed at Portsmouth to await repair

                9th          Taken in hand for repair by HM Dockyard

                25th        Carried out post refit trials on completion of dockyard work.

                                Resumed Flotilla duties


November              Deployed with the Flotilla for minesweeping off coast of Belgium.

to                            (Note: Ships returned to Ostend to anchor each evening.)



1 9 4 5


January                  Transferred to Harwich for mine clearance in southern North Sea.

to                            (Note: Extensive minelaying was being carried out by E-Boats and midget submarines

February                to disrupt passage of military convoys to ports in Belgium for support of

                                military operations. See HOLD THE NARROW SEA by P Smith.)

                                Returned to Downs anchorage overnight and every 10 days individual ships returned

                                to Base.

                                Nominated for refit.


March                    Under refit at Thames commercial shipyard.



                25th        On completion of post refit trials rejoined Flotilla at Harwich.


May                        Southern North Sea minesweeping in continuation.

to                            (Note: After VE Day Flotilla remained in Harwich for mine clearance.)




                26th        Sustained serious structural damage in collision with HMS HAZARD in North Sea.

                                (Note: Ships was holed below boat deck.)


August                  Passage to Thames to await repair in commercial shipyard.


P o s t   W a r   N o t e s


HMS JASON resumed Flotilla deployment for mine clearance in November 1945 on completion of repair. The ship remained in commission until 1946 when Paid-off at Portsmouth and placed on the Sales List. She was placed on the Sales list and acquired by Wheelock Marden &Co for use as a mercantile. Renamed JASLOCK this ship used in trade until 1950 when sold to T W Ward for demolition at Grays, Essex where she arrived in tow later that year.





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