After the records of the UK Singles Chart started in 1952 who was the first singer to be No 1?

Question

Who was Prime Minister of the UK on 28 March 1979, when the House of Commons passed a Motion of No Confidence, forcing a general election that was won by Margaret Thatcher?

Answer 1

Al Martino with "Here In My Heart"
The other three options were the first three at No 1 during the January following Martino's No 1 spot.