After a 10-minute delay to 6.31pm, the 2019 Senior TT winner opened up with a standing start lap of 130.37mph to go second fastest after Davey Todd shot to the top of the leaderboard on the Milenco by Padgett’s Honda, lapping at 131.66mph.
Todd stopped on his second flying lap, with Harrison going marginally faster than the 26-year-old to head the Superbike times on the third night of practice by 0.8s.
Ulsterman Michael Dunlop was third fastest on the Hawk Racing Suzuki, completing one lap at 129.119mph to clock his fastest time so far, with outright lap record holder Peter Hickman next on the Gas Monkey Garage BMW at 128.972mph.
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Ramsey’s Conor Cummins (Milenco by Padgett’s Honda) and 23-time winner John McGuinness (Honda Racing UK) were the top six, lapping at 128.721mph and 128.644mph respectively.
Newcomer Glenn Irwin increased his pace again to set his quickest lap so far on the Honda Racing Fireblade Superbike at almost 125mph, ending the evening 13th after a lap of 124.947mph.
Hickman, who did the first 130mph lap of TT 2022 on Monday evening before Harrison and Todd broke the 131mph barrier on Tuesday night, switched to his Superstock machine and did 130.032mph, completing two laps of the 37.73-mile Mountain Course.
Harrison was second fastest in the production-based class at 127.468mph ahead of Dunlop on his MD Racing Honda, who did 126.794mph.
Ian Hutchinson was fourth on the Milwaukee BMW (125.861mph) followed by Manxman and 2019 Manx Grand Prix winner Nathan Harrison on his Honda (125.367mph).
In the Supersport class, Dunlop did 125.94mph on his MD Racing Yamaha to knock Lee Johnston off the top spot.
Fermanagh’s Johnston went out for two laps on his Ashcourt Racing Yamaha, upping his pace to 124.44mph.
Harrison then went second fastest on his 600 Kawasaki at 124.817mph, with Johnston slipping to third.
The Superbike and Superstock session was suspended with around seven minutes to go due to a non-racing medical emergency, which required an ambulance to go onto the course.
A short delay followed before the Supersport and Supertwin session got under way.
Jamie Coward led the Supertwins on his Kawasaki (119.77mph) from Hickman on the VAS Engine Paton (118.8mph).
The session was later suspended after an incident at Laurel Bank involving Dave Moffit, leading to a delay of around 30 minutes before a one-lap Sidecar session got under way.
Favourites Ben and Tom Birchall were fastest on their LCR outfit at 115.66mph.