Lamont admits he mistakenly thought his team had been knocked out after last weekend’s agonising 13-12 Pool B defeat to Argentina.
He was granted a reprieve, however, when he was reminded that the Scots can still qualify for the last eight by beating England.
And Lamont will be heartbroken all over again unless they can manage the eight-point victory necessary to uphold their record of always reaching the quarter-finals.
“I honestly thought we were gone after the Argentina game. I didn’t realise we still had a mathematical chance of going through. Getting another lifeline is a massive relief and there’s no better game in the World Cup for a lifeline,” he said.
“A win without an eight-point margin is a loss as far as we are concerned. We know the job we need to do, but it’s still a lot of pressure. None of the boys are ready to go home yet. None of them.”
It is 25 years since Scotland enjoyed such a winning margin against the Auld Enemy and 40 since they scored four tries against them – the other way they could sneak into the top two pool places.
But Lamont, who has been shifted from wing to inside centre in a side featuring six changes, is taking heart from Scotland’s strong recent record against England away from Twickenham.
He added: “England are a great attacking threat. We know what they’re capable of. But away from Twickenham I think results favour us. Let’s hope it does again this weekend.”
Captain Alastair Kellock, Euan Murray, Richie Vernon, Mike Blair, Simon Danielli and Joe Ansbro return.