I have now got further information from Kalle Scheuch from the Foerderverein Museums Schnellboot. He writes "The two boats sailing to and mooring at Felixstowe Harbour on 13th May 1945, nine days after the partial capitulation of the Wehrmacht in Netherlands,
Northwest-Germany and Denmark on the 4th of May, were S 204 and S 205 from the 4th S-Flotilla. Prior to that event they had been captured by the British forces in Rotterdam/NL. That also explains the presence of British officers on board while crossing the Channel (see picture 2 of 12) and the fact that the boats were sailing under the White Ensign (see picture 10 of 12). The name of the Admiral they transported was Kontradmiral Erich Alfred Breuning. He was embarked in S 205. S 204 had on board KKpt Kurt Fimmen (Chef of the 4th S-Flotilla) and KptLt Bernd Rebensburg (Ia Op [Operations-Officer] of the Staff of FdS). The CO of S 205 was Kaptlt. Hans-Jurgen Seeger (see the sign HA-JU on the bridge). From the documents which I hold it seems that CO of S 204 was Lt.z.S. Claus Hinrichs, but that does not explain the sign "Lang" on its bridge.

Most of these photos were taken on the 13th May but some were taken shortly afterwards."S" boats were often referred to as "E" boats by the British. The "E" stood for Enemy, the "S" stood for the German word Schnellboot. Fast Boat.