A man called "Ricky" who bought drugs on the street turned out to be an undercover policeman.
The officer told Bristol Crown Court he paid £15 for two wraps of crack cocaine in Weston-super-Mare.
It is claimed the drug supplier was Dennis Rollinson.
Rollinson, 38, of All Saints Road in Weston-super-Mare, denies supplying a Class A drug in September last year.
Five men put behind bars after £112million stash of cocaine found on yacht
Speaking behind screens, the officer told the court he was using recording devices when he contacted a telephone number he had obtained and said he wanted to order drugs.
He told the court he was directed to the Montpelier area of the seaside town.
Ricky told the jury: "I recognized that as an area frequented by Class A drug users.
"When I arrived I recognized three people who were Class A drug users."
Man attacked four people on the streets with knife and bottles
The undercover officer said he then made a third telephone call and ordered two street deals of crack cocaine.
Shortly afterwards a man arrived and Ricky handed him a £10 note and a £5 note in exchange for two wraps of crack cocaine.
The jury watched cover camera footage the officer captured of the man who sold him the drugs.
Tony Bignall, defending, put it to him that he was mistaken that his client dealt him drugs.
But the officer was adamant that the man he captured on film was the dealer.
The case contnues.
