Johnson is delighted to take advantage of Dunlop's misfortune
Michael Dunlop looked to have yesterday evening's Superbike Classic TT race wrapped up when he held a 13-second lead at the Bungalow on the fourth and final lap.
To finish first, however, first you have to finish. The Ballymoney man was forced to retire two miles from the finish at Hillberry, and that handed Australian David Johnson (Kawasaki) his maiden victory by 41 seconds.
Dunlop, riding the Team Classic Suzuki XR69, led from the start until his scheduled pit stop at the end of lap two when he changed his rear wheel. That ate up time, and Johnson took advantage to lead at Glen Helen on lap three by 1.755 seconds.
Dunlop was back in front with a 3.7-second advantage by Ramsey and kept increasing his lead until he was forced to retire so close to home.
Derek Sheils came with a late surge in the final few miles to snatch second position from James Hillier by one and a half seconds, his first time on the Mountain Circuit podium.
Johnson said: "I knew Michael had a bit of an edge and it's unfortunate for him, but I'll take it.
"I saw him at the side of the track and I nearly lost the plot. I managed to hold it together to the chequered flag. To get a rostrum at the TT and a win at the Classic TT is amazing."
Sheils was equally happy. He said: "It is a great feeling to get directed into the winner's enclosure for the first time. The race was okay, although I had a bit of arm pump on the second lap.
"On the last lap I knew I was in fourth at Ramsey, so I gave it all I had over the mountain, hit the apexes and just kept the head down. To see the second-placed board shifted from James (Hillier) and placed in front of me was an incredible feeling."
Paul Jordan, Michael Rutter and Gary Johnson were retirements.
Earlier, after a four-hour delay due to low cloud, the Junior Classic TT got proceedings under way and saw a first Mountain Circuit win for a tearful Jamie Coward (350cc Honda) after three laps.
Maguiresbridge rider Lee Johnston (John Chapman Honda) came out all guns blazing to lead at Glen Helen on lap one.
With a 103.38mph opening lap, he led Coward by nine seconds with Dominic Herbertson third and Rutter fourth.
Drama on lap two saw Johnston retire at the Gooseneck, which left Coward with a healthy lead that he held until the chequered flag. He won ahead of Rutter, who nicked second from Herbertson on the final run over the mountain with Sheils fourth.
In a parade lap, Jamie Hamilton, badly injured in the 2015 TT, completed his first lap on a bike since then and Glenn Irwin, a possible TT entry in 2020, also participated.