In fact it was Thatcher. Reduced it from 33 to 30% and then gradually each successive budget - 29%, 27%, 25%. And top rate was cut to 40% (from 60%). To get votes.
As a teenager in the mid 1970s, everyone paid 33 1/3% income tax. Life was good. Wages were good, jobs were easy to get, and university education was free. It was conservative governments who reduced income tax for votes, and introduced stealth taxes.