He was born in Maffra to banker William Borthwick and Ada Maud Bell.
He worked for the Standard Bank of South Africa for a decade after leaving school, and in 1911 returned to Victoria to farm at Fulham.
During World War I he served with the 8th Light Horse Regiment at Gallipoli and was wounded at the battle of the Nek; he also lost an arm in Palestine at the battle of Romani.
After the war he farmed at Kilmany and in 1926 co-founded a stock and station agency based in Sale.
In 1938 he won a by-election for the Victorian Legislative Assembly seat of Gippsland North, representing the Country Party.