From a wealthy family, he began racing in the late 1940s, competing in his first event the Eastbourne Rally in a Healey.

[1][2] Downing switched to single seaters in 1952, racing a Connaught A-Type, and won the Madgwick Cup at Goodwood and second place at the Grand Prix des Frontières at Chimay, where he lost the lead at the end of the race several metres before the finish line.

[3] He finished ninth in the British Grand Prix at Silverstone, but had run fourth in the race before spinning while avoiding a backmarker.

[2] He competed in the Dutch Grand Prix later that year, but retired from an oil-pressure problem.

[4][5] His daughter Anne married Patrick McNally, whose company Allsport Management controlled the corporate hospitality and advertising for Formula One.