A member of the talented and gifted Uwchlawffynnon family, Sir David was born and bred in Llanaelhaearn. After leaving the local village school andPwllheliCountySchoolwhere he lernt to speak English he won a scholarship to theUniversityofWales Aberystwyth. He graduated with a First Class Honours degree in Economics. During the First World War he saw service with the Royal Welsh Fusiliers and afterwards he studied atPeterhouseCollege,Cambridgewhere he became an honorary fellow in 1956.
In 1920 he become a lecturer in law at Aberystwyth and was called to the bar in 1922 by theInnerTemple, of which he became a bencher in 1952 and took silk in 1955. In 1925 he married Haf the daughter of Sir O. M. Edwards, they had no children. Haf inherited her family home at Llanuwchlyn and they made this their home when inWales.
He lectured in law at the London School of Economics between 1924 and 1930 and became a professor of English law in 1930. Here he built a law department second to none in the country. At theUniversityofLondonhe created theInstituteofAdvanced Legal Studieswhich became an international centre for legal research. He was its part time director from 1947 to 1959.
Another important appointment was as Chairman of the Committee on the legal status of the Welsh language from 1963 to 1965 they reached a compromise that Welsh should have equal validity with English.
During his lifetime he held many high offices, he was knighted in 1951
After his retirement in 1959 he returned toWalesto live and died at his home in Llanuwchlyn.