Dean Harrison eased to his first Superbike win in the Isle of Man Senior TT after beating long-time leader Peter Hickman, whose BMW developed a late fault.
Hickman looked on course to secure his sixth TT win, having led by 20 seconds on the fourth lap, but was overhauled by Silicone Engineering Kawasaki's Harrison after the Smiths machine hit mechanical troubles.
A triple winner this week, Hickman was forced into running his Superbike - which he suffered issues with in last Sunday's practice - for the Senior instead of his preferred hybrid Superstock machine.
The Smiths rider led Harrison by 0.3s on the run to Glen Helen on the opening lap, and was a second clear at the Bungalow.
Hickman extended his lead to more than two seconds as he passed the Grandstand to start his second tour, and was eight seconds clear as the riders entered pitlane for their first stops at the end of the lap.
Harrison's deficit to Hickman continued to increase across the third tour, with the gap close to 20s by the time they came in for their second pitstops on lap four.
However, Hickman's lead was slashed to just 7.9s at Glen Helen on lap five, and a lowly top speed of 159mph compared to the 191mph for Harrison through the Sulby speed trap confirmed the BMW had developed an issue.
Harrison was just 1.1s behind at Ballaugh, and took over the lead at Ramsey by 7.8s, extending this to 18.3s over the mountain to start the final lap.
The Silicone Engineering rider would be unchallenged to the finish, Harrison cruising to his third TT win - and his first of the week - by 53s.
Hickman's issues allowed Padgetts Honda's Conor Cummins to reel him in over the final two tours, but Hickman managed to hold onto second by 5.8s.
Michael Dunlop ended a tough TT fourth on the Tyco BMW, with Bournemouth Kawasaki's James Hillier 63s further back to complete the top five.
Davey Todd was sixth on the Penz13 BMW to conclude his sophomore TT, beating the Bathams Honda RCV-mounted Michael Rutter, Jamie Coward (Prez Racing), ON-1 Racing's Brian McCormack and Dominic Herbertson (Davies Motorsport).
John McGuinness's Norton expired at the Bungalow on lap one, while Honda duo Ian Hutchinson and David Johnson were retirements on the second tour.
Supersport race winner Lee Johnston was a non-starter on the Ashcourt Racing BMW.