Career
L'Estrange was elected to Westmeath County Council in 1942, and served on that body until 1981 – one of its longest records of service. He was Cathaoirleach (Chairperson) of the Council for three years from 1959 to 1961 and served on virtually all the subsidiary and other bodies to which the council made appointments. He was chairman of the General Council of County Councils (Ireland) on three occasions, now known as the Association of County and City Councils.
L'Estrange was unsuccessful Clann na Talmhan candidate for Dáil Éireann at the 1944 general election. In 1954 he secured election to the 8th Seanad Éireann on the Administrative Panel. He was re-elected in 1957 to 9th Seanad, and in 1961 to 10th Seanad.
After another unsuccessful candidacy at the 1961 general election, L'Estrange was finally elected to the 18th Dáil for the Longford–Westmeath constituency at the 1965 election, and was re-elected at each successive election until he retired from politics at the 1987 general election. L'Estrange was appointed Minister of State at the Department of the Taoiseach, a position which included the role of Chief Whip. When his party was in Government and was being attacked by Fianna Fáil on the draining of the River Shannon, he is reputed to have replied "If you can suck as well as you can blow, the Shannon will be drained by teatime".