Grimson remained on the run in the Third Reich, hunted by the Gestapo, but eventually disappeared probably having been captured and murdered by the SS in or after mid-April 1944 in the Danzig area.

Grimson abandoned his architectural studies to join the RAF in early 1938,[2] in order to help support his mother and siblings after their father died in 1937.

37 Squadron RAF and commenced flying operational sorties in Vickers Wellington bombers at the outbreak of war.

Unlike his later more sophisticated escapes Grimson simply kicked his German guard in the backside and ran, but he was quickly recaptured.

[11][12] In September 1942 Grimson made his first solo escape attempt when he noticed that the German in charge of the stores where he helped out, looked very similar to himself.

Outside the wire they changed into civilian clothes disguised as foreign workers, walking to Sagan station and catching a train to the outskirts of Leipzig before being caught.

[14][15] In the late Spring of 1943 he made another attempt which was foiled before hatching a scheme to dress up as a guard with a fake rifle and march four prisoners out of the camp.

Wearing German overalls and leather belt pretending to test the boundary lighting, with a large ammeter fashioned from tins and dangling leads.

Whilst the prisoners were preparing to transfer he stole a ladder setting it at a point 10 feet from a guard machine gun tower, calling up to the guard in fluent German he stepped over the warning wire and used his ladder to climb up to the lights, placing a plank across the two barbed wire fence lines.

[17] Arriving in Danzig (Gdańsk) he renewed contact with the Polish underground and organised a courier system using Germans on the Tally-Ho payroll.

[19] Harold Bennett quotes in his Official RAF liberation questionnaire that he was "a member of the Tally-ho club in Sagan and Heydekrug and helped to gather information and escape kit together.

[20] Grimson was supported by anti-Nazi Germans, forced labourers from German-occupied countries and a network of informants but was constantly hunted by the Gestapo agents of SS-Obersturmbannführer Dr. Günther Venediger,[21][circular reference] a price was placed on his head and wanted posters printed.