Found it. The convoy in question was OG (Outbound Gibraltar) convoy. Spoiler alert:
Since, to my knowledge, these convoys were heavily guarded, I would recommend to vdr1981 increasing escorts for this group type. In fact, just checked and there was equivalent historical convoy (OG 63, sailing in late May-early June 1941) that had 9 escorts assigned with 6 more joining in after it was attacked by U-Boats (EDIT: scratch that last sentence, more escorts actually joined before the attack).