Welcome aboard Rolf - hope that you enjoy what the site has to offer.
For starters - This boat was ordered in November 1940 as a Motor Anti-Submarine Boat (MASB) but was completed as a Motor Gun Boat (MGB). It was converted for use as a Motor Torpedo Boat (MTB 415) in September 1943, survived the war, and was placed on the disposal list in October 1945. She had the alternate Pennant of MGB 80 (from our Boat Database
1st MTB Flotilla: From December 1939 - 1942 after returning from the Mediterranean operated from Portsmouth, Felixstowe and Harwich, then owing to losses was disbanded in August 1942. Reformed in October 1943, then until 1945 operated from Dartmouth, Ramsgate, Portsmouth, Lowestoft and Felixstowe. From those dates you can see that the 1st Flotilla was a very mobile unit. The re-formed unit had 4 Senior Officers; Lt EN Stephenson RN. Lt TJ Mathius RNVR. Lt J.A. Bennet RCNVR. Lt CEM Thornycroft RN.
“Home Waters MTB’s at War” by Leonard Reynolds has a photograph of MTB 415 on page 119 alongside HMS Aberdonian at Dartmouth (while there are a few, relative expensive copy’s for sale at Amazon, a good Library may be able to loan a copy) there is just one mention of action with MTB 415 in that book
“…The new 1st Flotilla cut its teeth on the 26/27 February when 415 and 431 (both without Tubes), led by Lt T J Mathius, maintained the traditions of Hichens’ 8th MGB Flotilla when they attacked a convoy entering harbour in Jersey, and claimed to have severely damaged a trawler…
As you can see the 1st Flotilla had two 'beginnings'. The Flotilla, just pre-war, was ordered back from the Mediterranean, to the UK just as hostilities commenced (that story is in itself a gripping saga) arriving back during December 1939.
I would guess that our members may be able to furnish you with some further info.
(Just type MGB 609 in the Search panel at the top of this