The Duke of Cambridge met a trainee lawyer on Monday who had been awarded a scholarship established in honour of the royal and found himself discussing superbikes.
William swapped stories about the powerful road machines with fellow enthusiast Steven Kennedy, who hopes to become a barrister thanks to the STG25,000 ($A40,000) award.
The pair met at Middle Temple - one of the ancient Inns of Court in central London - where the Duke is an honorary barrister and member of the institution's governing body.
William was making his first public appearance in the UK with Kate, since the controversy over the Duchess' topless pictures broke last month.
The royal couple have a series of engagements this week but it was announced earlier that William will miss a number of events in the Newcastle area on Wednesday, as he has to attend the funeral of Olga Powell, the Duke and Prince Harry's nanny for much of their childhood. She died last month.
Kennedy, 40, is fulfilling a life-long dream to become a barrister and earlier this year received one of two Duke and Duchess of Cambridge Scholarships, established by Middle Temple to mark the royal couple's wedding last year.
He said: 'They were a very nice couple and I ended up talking with the Duke about our love of motorcycles.
'I'm not that tall but when I get off the bike I feel a bit sore because you ride hunched over, but William was saying when he gets off he has to straighten himself out and get all the kinks out.'
Mr Kennedy from Stratford, East London said: 'He's got a Ducati 1198, which can probably do 170 or 180 miles per hour (about 280km/h). I've got a Suzuki GSXR 600 and I've had that up to 157 miles (252km/h) on a race track.
'My girlfriend rides a (Kawasaki) ZZR 1400, which can do about 187mp/h, and he said 'she must be a better rider than you' and I said 'yes she is'.'