On a balmy evening at Barcelona's Olympic Stadium, Chris Thompson made it a British one-two as he held off Italian Daniele Meucci, although they were both given the same time. Britain was not the only nation to enjoy a one-two on the opening day of the championships.
Belarus took the top two places in the women's shot put final through Nadezhda Ostapchuk and Natallia Mikhnevich.
Cheered on by a sparse but noisy crowd, waving red and yellow Spanish flags, Moroccan-born Lamdassem hit the front in the 10,000 metres with three laps to go but could not sustain the tempo and eventually finished a disconsolate fourth.
Somali-born Farah, silver medallist in the 5,000 at the 2006 Europeans, kicked hard just after the bell as he and Lamdassem were lapping stragglers and the Spaniard had no answer to the Briton's sudden injection of pace.
The goatee-bearded 27-year-old pulled clear and crossed the line with his arms outstretched with joy to win in 28 minutes, 24.99 seconds.
"I can't quite believe it. It's not been easy," said Farah who was given a Union Jack with the words 'Fly Mo' on it after he crossed the line.
World indoor shot put champion Ostapchuk went one better than her European silver of four years ago with a best effort of 20.48 metres in the final. The Belarussian, who led from her opening throw of 19.67, beat compatriot Mikhnevich in a reverse of the 2006 result.
Anna Avdeyeva prevented a Belarussian clean sweep when she threw 19.39 on her final attempt to take the bronze ahead of Yanina Pravalinskay-Karolchyk.
Olympic and world champion Olga Kaniskina led the Russian sweep of the medals in the women's 20km walk on Wednesday.
Kaniskina led compatriot Anisya Kirdyapkina by 10 seconds at the halfway mark and continued to pull away from the field to win in a time of one hour, 27 minutes and 44 seconds.
Kirdyapkina, fastest woman in the world this year, was a distant second, one minute and 11 seconds behind. Vera Sokolova was third.
David Greene, the clear favourite for the men's 400 hurdles, was untroubled in his heat before winning in 50.11. Greene is the only European to go below 49 seconds this season.
But defending champion Periklis Iakovakis of Greece showed he could be coming into form with a season's best of 49.49 to finish second in his heat behind Briton Rhys Williams.