Walmsley was passenger to Pete Founds at the world-famous motorcycle meet and negotiated the notorious mountain course to finish in a superb second place.
The 26-year-old was named fastest newcomer at the TT to earn the Dave Wells Trophy and joins an elite list of passengers to exceed an 112mph average lap time.
With Founds only in his second attempt at the TT and Walmsley a novice, the team were allowed to get an early sighting lap on the Saturday ahead of Monday practice.
Their first lap together in anger was not without incident as an unsuspecting brush with a wall at Tower Bends, one of the slower parts of the track, doing significant damage to the bike.
The team worked hard on repairs and gradually got quicker during practice week. The pair posted laps of 107 and 109mph on Tuesday, gradually improving to two laps at an impressive 112mph average on Friday.
The opening lap of Saturday’s race saw Founds and Walmsley impressing in fifth place and then benefited from a retirement to move up a place on the following lap.
The second lap was also memorable for a new sidecar TT lap record of 116.798 mph by leaders Ben and Tom Birchall.
The Birchall brothers’ lead grew at both Glen Helen and Ballaugh Bridge, but on a dramatic final third lap the pair had to retire at Sulby Crossroads.
Having already gone past Tim Reeves and Patrick Farrance, Founds held off the challenge of his brother Alan and Aki Aalto to finish a magnificent second behind winners John Holden/Andrew Winkle.
Confidence was high for Friday’s second race after their unexpected result in race one.
But their luck ran out and they were forced to retire at the end of the second lap while running in sixth place.
Attentions will now turn to the British F2 Sidecar Championship which Founds and Walsmley lead going into the third round at Anglesey this weekend.