By Neil Maidment

LONDON (Reuters) - Mo Farah became Britain's first men's 10,000 meters Olympic champion on Saturday, delivering on huge pre-Games expectations in front of an ecstatic home crowd who roared him every step of the way.

The 29-year-old, who also became the first man to win this event on home soil, won with a time of 27 minutes 30.42 seconds, half a second ahead of his training partner Galen Rupp of the United States who grabbed a surprise second place.

Ethiopia's Tariku Bekele took bronze with his brother Kenenisa, who was bidding for an unprecedented third 10,000m Olympic gold, in fourth.

In a nervy race it took until the final lap for Farah to break away, finding an extra boost of energy on the last bend that took him far enough away from Rupp and over the line to a raucous reception.

Farah dropped to his knees on the track in elation before rushing to embrace his daughter and pregnant wife.

Rupp became the first American to win a medal in the event since Billy Mills won it in 1964 in Tokyo.

(Editing by Ed Osmond)