Frederick Archibald de la Mare (universally called 'Froggy') was born on 6 August 1877 at Christchurch, New Zealand. His parents were William Henry de la Mare, a grocer, who had emigrated in 1864 from Guernsey in the Channel Islands, and his wife, Elixa Wilson, who was born in Edinburgh, Scotland, and was brought to New Zealand at the age of four.
After receiving his education at Sydenham School and Christchurch Boys' High School de la Mare entered the civil service in Wellington in May 1896 as a clerk in the Department of Labour, then transferred to the colonial secretary's office in June 1902. He enrolled as a student at Victoria College and graduated BA in 1904 and LLB in 1912. The college (later Victoria University of Wellington) retained de la Mare's lifelong loyalty. He poured out his affection in many ways, not least in the editing in 1910 of a collection of verses (including a selection from his own student writing) composed in and around the college. Under the cheerfully affectionate title The old clay patch, the collection went into two further editions, in 1920 and 1949. De la Mare was editor of the student magazine Spike in 1903–4, president of the students' association in 1906, and elected a life member in 1911.
De la Mare married Sophia Ruth Child, a medical practitioner, in Sydney, Australia, on 25 April 1914 and moved to Hamilton where he set up a law practice. In 1916 he enlisted for war service. He was gravely wounded at Passchendaele (Passendale): most of his right hand was paralysed and almost to the end of his life his leg bore some of the shrapnel that had cut him down. Leaving the army in 1920, de la Mare returned to resume his practice in Hamilton. He was a reluctant lawyer, but a trusted confidant and adviser to his clients, particularly those who could ill afford the cost of professional services. Many of them lived a great distance from Hamilton: de la Mare would visit them in their homes, travelling by bicycle over rough country roads. He looked on his clients as friends to be helped. Where he sensed injustice, he was tireless in his efforts to find a remedy.
He was an ardent exponent of penal reform and vigorously advocated measures for the rehabilitation of prisoners. His zeal sometimes made him unpopular with officials in the Department of Justice and, on one occasion, led him into a wounding controversy with an old friend, the judge H. H. Ostler, concerning the functions of the Prisons Board. De la Mare was active in the New Zealand Howard League for Penal Reform, becoming dominion vice president.
Frederick de la Mare was a public educator par excellence. He maintained a lifelong concern for academic principles and, in particular, for academic freedom. During the First World War he publicly criticised official interference in university matters, especially the government actions leading to the dismissal of G. W. von Zedlitz as a professor at Victoria University College. He returned to that theme in 1935 when he wrote his pamphlet Academic freedom in New Zealand, 1932–34, in which, with measured analysis, he exposed the unworthy motives which led to the termination of the historian J. C. Beaglehole's employment at Auckland University College.
In 1920 de la Mare was elected to the Senate of the University of New Zealand as a representative of the graduates. Over the next 28 years he vigorously advocated the development of a second medical school, full-time university study as compared with the part-time study that was a standard feature of university life at the time, and the complete independence of university teaching and courses from professional pressure.
De la Mare had a passionate love of sport, but always as an amateur. Professionalism in sport was obnoxious to him, as was the notion of winning at all cost. At secondary school he had excelled in athletics, and he was a university representative in rugby football, cricket, and tennis.
His concern for the public good was shown in his enthusiasm for many public causes. He was a lifelong total abstainer from alcohol and became a vigorous campaigner for prohibition: he was a member of the dominion executive of the New Zealand Alliance and dominion president in 1950–51. Prohibition sentiment at the time was based almost exclusively on religious conviction, and the election of de la Mare, a well-known rationalist, was a remarkable personal tribute. He was also, on ethical grounds, strongly opposed to gambling, and was particularly critical of the laissez-faire attitude of the Anglican church.
Underpinning de la Mare's commitment to the public good was an unshakeable commitment to high moral standards. As a young man he had been a member of the Unitarians and later of the Forward Movement; but subsequently became a freethinker and a rationalist. He was a frequent contributor to the New Zealand Rationalist. He strongly opposed the Bible in schools movement and also any suggestion that the university should countenance courses leading to theological degrees. His attitudes to moral questions were based on rationalist principles, although he was prepared to accept the support of religious arguments in the common cause.
He was an ardent supporter of the League of Nations and of the ideals and principles of the United Nations. At the time of the Munich Agreement in 1938 he was among the few who condemned the treachery it involved. He spoke out on behalf of refugees, particularly those from Nazi Germany, and as a member of the Senate of the University of New Zealand argued against their exclusion from the provisions of the ad eundem statute, which recognised foreign academic qualifications.
De la Mare remained a sole practitioner in Hamilton for almost 30 years until he was joined by D. D. McLeod in 1949. On his retirement he moved to Eastbourne, Wellington, where he died on 9 May 1960. He was survived by his wife and their two children, a son and a daughter. De la Mare was a man of strong physique, huge and spare-limbed in appearance, a formidable opponent in controversy as in sport. A man of moral earnestness and a powerful debater for causes in which he believed, he despised debating for its own sake. He had a great gift for friendship and was remarkably kind-hearted to anyone who needed his help, no matter what their circumstances.