Apparently they were used to destroy the E-boat pens in Boulogne to make they would be in a disadvantageous position come the Normandy landings.
15 June 1944 – Boulogne harbour
297 aircraft: 155 Lancasters, 130 Halifaxes, 12 Mosquitos, of Nos 1, 4, 5, 6 and 8 Groups attacked Boulogne harbour...