Michael Dunlop broke his own race record from 2013 by over a minute as he won the delayed Formula 1 Classic TT.
Riding a Team Classic Suzuki, Dunlop posted a fastest lap of 125.050mph on his final circuit, to come home ahead of Bruce Anstey and Ryan Farquhar.
Dunlop and Anstey had been battling for the lead throughout but the Kiwi's challenge for the win ended when he was black-flagged for a loose exhaust.
Manxman Ryan Kneen won the concurrently run Formula 2 race from James Cowton.
Kneen enjoyed a commanding victory, breaking the previous lap record by a minute.
Anstey, riding a Yamaha YZR 500 V4, lay seventh early on in the race, but led by less than a second by the end of the opening lap.
The New Zealander had extended his lead to 12 seconds at the end of lap two, courtesy of a new lap record of 126.26mph, the first sub-18 minute Classic TT lap at 17:55.769.
Anstey lost 15 seconds to Dunlop in the pits and the Northern Irishman assumed the lead, but the spectators were denied a thrilling finish when the Yamaha rider was black-flagged at Cronk Ny Mona because of a loose left exhaust.
The Valvoline Padgett's rider lost 59 seconds in the pits while his pit crew fixed the problem, handing victory to Dunlop.
Anstey recovered, however, to snatch second place from Farquhar by a second.
Meanwhile, Michael Rutter won the delayed 350cc Classic TT in near perfect conditions on the Mountain Course.
Dan Cooper led the race by over a second entering the final lap on his Team Molnar Manx Norton before retiring at Ballacraine.
His retirement left Rutter with a commanding lead of over a minute which he held to the finish on the Ripley Land Racing Honda.
Leading privateer Philip McGurk finished second with Doug Snow completing the podium.