Gretton mounted a vigorous defence as the U-boats attacked after dark. At 2000 "Sunflower" detected a radar contact at ; and upon closing lost the radar contact, gained a doubtful ASDIC contact, and dropped two depth charges. At 2245 "Duncan" detected a radar contact at ; and upon closing lost the radar contact, gained an ASDIC contact at , lost contact at , and dropped one depth charge. Upon returning to station "Duncan" detected a radar contact at ; and upon closing sighted a U-boat which dived at , and appeared on ASDIC at . "Duncan" dropped a pattern of ten depth charges; and, while turning for another attack, gained another radar contact. The radar contact disappeared at a range of . "Duncan" made no ASDIC contact, but dropped a single depth charge at the estimated diving position before making another radar contact at . As "Duncan" closed, the U-boat dived at a range of . "Duncan" gained a good ASDIC contact and dropped a pattern of ten depth charges over a visible wake. Two more depth charges were dropped when a weak ASDIC contact was regained at 0045. At 0132 "Snowflake" approached a hydrophone contact, and "U-532" was detected visually and on radar at a range of . "U-532" launched six torpedoes. The closest one missed "Snowflake" by about . After "U-532" dived, "Snowflake" dropped three depth charges on the initial ASDIC contact and ten depth charges when contact was regained at . "Snowflake" regained ASDIC contact at and dropped another pattern of ten depth charges. A short time later "Tay" dropped depth charges on a good ASDIC contact astern of the convoy. "U-532" returned to base to repair depth charge damage. "U-386" and "U-528", were also damaged by these attacks and forced to return to base. "U-386" arrived safely at St Nazaire on 11 May, but "U-528" was attacked in the Bay of Biscay and sunk by aircraft on the same day.