Captain Courtney Lawes was the beneficiary of a fortuitous bounce off Marler’s bonce, collecting the loose ball and grounding beneath the posts for a crucial second try.
England subsequently scored twice more late on to secure a 34-12 bonus point victory.
Although the ball travelled forward, as it came directly off Marler’s head it was not knocked on, and with Lawes in an onside position when contact was made, the try was upheld by the television match official.
England have been playing football regularly in training at this tournament, including at their captain’s run on Saturday, and Marler quipped afterwards that the hard work had paid off.
“It’s just what I’ve been practising for, these moments,” Marler said. “I practised it today with Dan Cole and Jamie George – in activation, we were practising our headers.
“I took huge inspiration from Robert De Zerbi’s mighty Seagulls, doing a demolition job on United, which is my son’s team. Four Premier League games in a row. Only three teams in Premier League history have beaten Man United four Premier League games in a row: Brighton, Man City and Liverpool.
“But [Brighton have] won nothing yet guys – which brings us right back to us, because we’ve won nothing yet. We’ve had two good victories, one in different circumstances and we’re on to the next.”
England are top of Pool D after their opening two fixtures, and next face Chile in Lille on Saturday before concluding their pool efforts against Samoa a fortnight later in the city.