Hours later, just after midnight, he fulfilled his promise, posting a picture on Twitter of himself at a rooftop bar at St Pauls.
"Getting wasted at at (sic) StPauls," read the caption – his spelling and grammar seeming to suggest he was well on the way to achieving his aim.
An hour later he called it a night, however, telling his 300,000 followers: "Well what a day, blind drunk at the minute and overwhelmed with all the messages, Thank You everyone it's been emotional X"
The Londoner took gold in the time trial after previously declaring it would be "a doddle".
Fears he would be too tired to take the top spot after completing 2,200 miles last month in the Tour de France turned out to be unfounded.
He whizzed through 27 miles of the Surrey countryside, beating his nearest competitor, German rider Tony Martin by 40 seconds.
Taking the bronze, meanwhile, at the Hampton Court finish was fellow Brit Chris Froome.
There were echoes of Bradley's French win as he took to the winner's podium to collect his medal amid cheers and the fluttering of red, white and blue flags. And even the sun came out.
Just as in Paris, Bradley's wife Cath and his children Ben and Isabella were waiting to shower him in congratulatory hugs and kisses.
The 32-year-old has now beaten Sir Steve Redgrave's record as Britain's most decorated Olympian. He has won four golds, one silver and two bronze medals.
Sir Steve, who still holds the records for the most gold medals – with a haul of five gold and one bronze – was quick to praise Bradley.
The retired rower hailed his cycling triumph as an "outstanding achievement".
Steve, who donned stick on sideburns in the spirit of fun for a TV interview was asked his thoughts about Bradley being called 'the most successful Olympian'.
"How can you argue with that? He's a great guy, a great athlete and obviously he's got more medals than me.
"So to me, that put him above me on achievement level.
"If I'd won the Tour de France a couple of weeks ago and then come and won one of my medals, I would have been expecting to be above him on that.
"He's a great guy, absolutely outstanding achievement and he deserves all he gets. I think he's going to get a lot more honours before the year is over."