England manager Gareth Southgate revealed on Monday he once supported Scotland at the 1978 World Cup as the old rivals prepare to do battle in a friendly to mark the 150th anniversary of their first meeting.
Scotland have not beaten the Three Lions since 1999, but go into Tuesday's clash in front of a home crowd at Glasgow's Hampden Park full of confidence as they close in on qualification for next year's European Championship.
Clarke believes the test of facing England is a "benchmark" of how far his side have progressed.
And Southgate is looking forward to savouring the hostile atmoshpere at Hampden, despite having once had a soft spot for Scotland himself.
"This is horrendous, what I'm going to say here ahead of tomorrow, but I was supporting Scotland in 1978 because we hadn't qualified," said the England boss.
"Then we were back in in 1982 and all of a sudden for me then onwards it was all about England."
- 'Fabulous game' -
He added: "Great fixtures, I've met so many of the former players over the years, worked with some of them, played with some of them. It's a fabulous game.
"I know it's a rivalry and people will be wary of it crossing a boundary, but it's a brilliant sporting rivalry and a great game to be involved in."
Scotland's place at Euro 2024 could even be sealed while they are in action should Norway and Georgia draw in Oslo.
But Clarke insists his full focus is on ending his nation's poor recent record against their local rivals.
England lead the overall head-to-head 48 wins to 41, but have been even more dominant in recent times.
Scotland's 1-0 success at Wembley 24 years ago in a Euro 2000 playoff, which England still won 2-1 on aggregate, is the only time the Three Lions have lost in the last 12 meetings stretching back to 1986.
"Now we see what we can do against a team that's nominally a pot one team, always in the later stages of tournaments," said Clarke at his pre-match press conference.
"That's the benchmark we want to judge ourselves against and we will find out tomorrow night how close we are."
The sides last met at Euro 2020, when a group stage clash ended in a goalless draw.
England went onto reach the final of that competition, losing on penalties to Italy, while Scotland failed to make the knockout stage in their first major tournament for 23 years.
But Celtic midfielder Callum McGregor believes Scotland have made progress during the past two years.
"We are evolving all the time and we've had some big results since the Euros. We are looking really comfortable at this level, home and away. It's just another opportunity for us to show how far we've come," said McGregor.
"It's a great game for us to go and test ourselves. As a nation, if we want to continue to make the next step and continually qualify for big tournaments, these are the types of games we have to earmark for performances and results."