Farah (centre) and Kosgei made all the running around central London
Mo Farah smashed the British 10k record to win the Bupa London 10,000 road race in a time of 27 minutes, 50 seconds.
He knocked five seconds off the mark set in 1984 by Mark Scrutton to finish well ahead of Samuel Kosgei (28:03) and Sergiy Lebid (28:36).
Londoner Farah won the European Indoor 3,000m title in March, having previously broken the national record.
In the women's race, Briton Hattie Dean clocked 33.52 as she finished second behind New Zealander Kim Smith (31:38).
Romania's Olympic marathon champion Constantina Dita was third in 34:25.
Farah was content to share the pace with Kosgei after they broke away from the field before pulling clear of the Kenyan with 3km of the race remaining.
"I knew I was in really good shape," said the Briton, who has only recently returned from a high-altitude training camp in the French Pyrenees.
The 26-year-old added: "I wanted to win and to get close to 28 minutes so to get the British record is a bonus.
"Kosgei did hang on for a long time but I knew I could out-kick him. I wanted a decent time so after 7km I thought I'd get clear of him."
Farah will now turn his attentions to preparing for the IAAF World Championships in Berlin in August.
He is expected to open his track season over 3,000m in Turin on 4 June.