Mr Dearlove's friend Andrew Cook said: "He (Timon) was looking for a fight. We didn't know why, it all happened so quickly." Timon, from Plumstead, south-east London, who is mixed race, claimed one of Mr Dearlove's friends called him a "half chap".
Afterwards, he fled to Ireland to see his mother and sent a series of messages to a close female friend apologising for what happened before handing himself in to police.
Mr Dearlove, a relationship manager at Duncan Lawrie Private Bank, who had previously at Couttes, the bank used by the Queen, was eating and drinking with old University of Portsmouth friends in Blackheath, south-east London, on 27 August last year.
After a dispute erupted after a "polite" chat about baby pictures, Timon punched Mr Dearlove, who died about 24-hours later.
He told the witness, who cannot be identified, that he had "mad love" for her, saying: "I'm scared, seriously, proper. I'm sorry really from the bottom of my heart." He will be sentenced at the Old Bailey later this week.