He was Chief Government Whip from 1967 to 1969, and played a role in the ascension of John Gorton to the prime ministership after the disappearance of Harold Holt.

He enlisted in the Royal Australian Air Force (RAAF) in January 1940, training as a radio operator.

Gorton subsequently appointed one of his young staffers, Ainsley Gotto as his private secretary and came to rely on her for political advice.

His final political candidacy occurred at the 1979 elections for the Australian Capital Territory House of Assembly, where he ran unsuccessfully as an independent.

His second marriage also ended in divorce, and he married for a third time in 1977 to Gwendolyne Phyllis Potter (née Pennant).

After leaving parliament, Erwin split his time between Canberra and Caloundra, Queensland, where he owned a block of units.