Harry Howlett competed regularly through 1955, '56 and '57, initially in a Cooper Mk VIII JAP but in March 57, he moved to a Mk XI Norton. In June 1955 he finished sixth in the JAP Race in June, then fifth in the same race in July, both at Brands Hatch His most significant result was an impressive third place in the Commander Yorke Trophy in September at Silverstone. On 25th September, Harry won the Handicap Race at Brough followed by a sixth in the Second Final at Brands on 9th October to close the year.
1956 started well with a second to Don Parker at Brough on the 25th March then a respectable ninth in the Earl of March Trophy on 2nd April but could only manage sixteenth at Aintree on the 21st and the same position in the International Trophy at Silverstone. At Cadwell Park on 21st May, Harry won his heat and took fourth in the Final of the Sheffield Trophy and second in the Handicap Race. Back at Aintree for the Midsummer 100, he was down to thirteenth then failed to finish in the Grand Prix on 14th July and ninth at Snetterton on the 22nd. At Mallory Park on 6th August, Howlett took second place in the Consolation Final followed by a fine second to Henry Taylor at Silverstone on the 11th August then fourth at Silverstone on 6th October to close the season.
Now in the Cooper Mk XI Norton for '57, Harry took fourth place at Snetterton on 31st March then a sixth in the Earl of March Trophy on 22nd April and fourth at Snetterton in May. A third and a fourth came at Mallory in June then a fifth in August.