It was based at the port of Lowestoft and was originally ordered by the Admiralty as one of eight Round Table-class trawlers during World War II HMS Sir Lancelot (T228) took part in Operation Neptune, the D-Day landings in June 1944, attached to the 14th Minesweeping flotilla in Force U.

In respect of each of the five beach Assault Forces (designated U, O, G, J and S), two channels would be cleared through the mine barrier for the first wave of amphibious infantry.

[1] On 5 February 1945, HMS Sir Lancelot (T228) picked up survivors from the American merchant ship SS Henry B.

Plant, that was torpedoed and sunk by German submarine U-245, about 17 nmi (31 km; 20 mi) east of Ramsgate in position 51°19′N 01°42′E / 51.317°N 1.700°E / 51.317; 1.700.

[3] Datasets collected aboard the RV Sir Lancelot were instrumental in the ground-breaking book On the Dynamics of Exploited Fish Populations written by Ray Beverton and Sidney Holt in 1957.