He was a Labor Party member of the New South Wales Legislative Assembly from 1930 to 1932, representing the electorate of Ashburnham.
Keast was born at Creswick in Victoria, but moved with his family to Parkes at an early age.
[1] Keast was preselected to contest the newly recreated seat of Ashburnham for Labor at the 1927 state election, but was defeated by Edmund Best, then the MLA for Murrumbidgee.
He recontested the seat at the 1930 election, and defeated Best amidst Labor's landslide victory under Jack Lang.
His time in politics was to be short-lived, however; the Lang government was sacked by the state Governor in 1932, and Keast was one of many Labor MLAs to lose at the subsequent election.