During his long and extremely prolific academic career, he built the world's foremost representative collection of medieval coins, wrote very extensively on the subject, brought it to much wider attention in the historical community and filled important curatorial and teaching posts in Cambridge, Brussels and Washington DC.
However, his early interest in the sciences left him with a sound knowledge of the methods and principles of metallurgy, mathematics, statistics and much more besides that would prove valuable in later years.
Graduating with a double first, he took the Lightfoot Scholarship from the university and also won the Schuldham Plate, his college's highest academic accolade for students.
For many years already Grierson's interests had encompassed the medieval Low Countries, and he had a number of friends in Belgium, not least the great Carolingian scholar François-Louis Ganshof.
Work in the United States began in 1953, when Grierson was one of the founding instructors at the American Numismatic Society's annual summer school.
He returned the following year, and in 1955 was invited to become honorary adviser and curator at the Dumbarton Oaks Research Library and Collection in Washington DC, managed by the trustees of Harvard University.
His brief was to use the centre's considerable resources to build up the world's finest collection of Byzantine coinage and publish it – a task which, by the time he left the post in 1997, he had completed admirably (despite once accidentally dropping a tray of gold coins down a lift shaft).
The following Keeper of Coins and Medals, Mark Blackburn, first came to the department in 1982 as part of the Medieval European Coinage project to publish Philip's burgeoning collection.
Wartime and post-war conditions meant that these coins were available at a fraction of their pre-war (and equivalent modern) price, with heavy restrictions on the activities of foreign purchasers.
Grierson was a careful buyer, but could also be willing to spend significant amounts for particular coins, such as his famous and exceptionally rare portrait denier of Charlemagne.
He moved into St Michael's Court in the 1930s, and occupied the same set of rooms overlooking the Market Square in Cambridge after an interlude during the Second World War, when they were used by the Ministry of Agriculture, Fisheries and Food.
As a student and young fellow, Grierson had a great interest in and admiration for the Soviet Union, which led him to spend a summer touring it with a friend in 1932.
They were the father and father-in-law of David Daube, a friend of Philip and subsequently regius professor of civil law at Oxford.
Poor eyesight and a childhood injury left him unfit for military service, and despite being interviewed he was rejected from the Ultra codebreaking enterprise at Bletchley Park because his German was not strong enough.
Physical challenges appealed to him, such as when on one occasion in 1932 or 1933 he walked home from London one evening – a distance of some forty-four miles – and arrived the following lunchtime.
At Rugby, he caught the post train for Holyhead, and after catching a ferry the following morning made it to Dublin in plenty of time for his party.