AN AMERICAN who worked in England, Marcus Merriman is best remembered as an exceptional historian of sixteenth-century Scotland.

He was born in Baltimore, into a well-connected family among whose friends was Adlai Stevenson. His undergraduate education at Bowdoin College (Maine) included a year abroad at Edinburgh (1960-61), where he excelled in history and fell in love with Scotland's past. Subsequently he worked on Anglo-Scottish relations in the 1540s for a London University PhD, and in 1964 he was the first history lecturer appointed in the newly-founded Lancaster University.

Also in 1964, his first academic study, on Scots collaboration with England, won the Royal Historical Society's David Berry gold medal. In 2001 his last major work, the magisterial if delightfully idiosyncratic The Rough Wooings: Mary Queen of Scots, 1542-1551 (Tuckwell, 2000), was the Saltire Society's Scottish history book of the year.

In between, he made a major contribution on Scottish forts to the History of the Kings' Works, and published numerous articles about midsixteenth-century Scotland: on propaganda for British union, fortifications, mapmaking, Italian engineers, Scots exiles, and Mary "Queen of France".

All his work was based on ground-breaking research in Scottish, English and French archives; collectively, it hugely enriched Scottish history and pioneered a genuine British approach. In his long career at Lancaster (42 years), he was also outstanding as a teacher (winning national and university teaching prizes), college and union officer, and, until deafness intervened, prominent member of university committees.

That looks like a conventional academic success story but Marcus was anything but conventional. His writing involved deep research and brilliant insights, but also a zany prose style and a distinctly meandering technique.

His acknowledgements in Rough Wooings constitutes a six-page autobiography, thanking cleaners, newsagents and publicans as well as historians; his conclusion about the young Mary Stewart, "She was thus nothing less than the saviour of her country. Not bad for a babe", illustrates how he wrote. Sober editors might be driven to distraction, but his accounts of the past jump off their pages and grip their readers by the throat.

His teaching style was similarly inimitable. He was never happier than when he was declaiming - particularly, being an actor manque, in costume (either as Henry VIII or as a kilted BlackWatch officer).

The flavour of his lectures is encapsulated in the opening of his party-piece on Kennedy's assassination: "Everyone remembers what they were doing when they heard about JFK's death. I sure do: her name was Eleanor." After an on-song performance, enthralled audiences would seem to float out of the room.

Even his more routine course lectures were full of pyrotechnics: sometimes literally, for he regularly "illuminated" one on military history by igniting a basin of homemade gunpowder (until fire regulations intervened, whereupon he took to marching his students into the university's main square, and discharging his own cannon (fortunately not loaded with his own cannon-balls) towards the student union building.

There was a streak of selfindulgence in all this; but the main intention was to enthuse and inspire his students. That worked: for countless students, his courses were unforgettable. This applies especially to his final-year 'Special" (senior honours class) on Mary Queen of Scots. Enrolments were invariably in the teens, unusually high for this type of sourcebased course; so, in all, he taught it to well in excess of 400 students.

Nowhere else, even in Scotland, can a Scottish history topic have been taught at that level to so many students - and they were predominantly English. He gave them a profound understanding of a pivotal era of Scottish history, and also a broad appreciation of Scotland as a whole - cemented by his Easter field trips, when they swept round more than 80 historical sites in under a week. His selling of Scottish history to all these English students was just as important for the subject as his publishing.

Alas, as with most flamboyant characters, there were downs as well as ups, especially after his divorce and the tragic death of his son - and Marcus never did anything by halves. Among the Scottish products he appreciated was whisky, among the American, tobacco; both, ultimately, undermined his health.

Yet while, as a result, he was sometimes an infuriating colleague in his later years, he was invariably forgiven and understood. This is, I believe, because of his constant, if occasionally overwhelming, kindness and goodness (though academics are given to gossip and cattiness, I never heard him be nasty about anybody). That he could continue to be so unconventional in a profession where convention and box-ticking is increasingly obligatory was due, above all, to that magnanimity, or great-heartedness though eventually his heart let him down.

He is survived by his partner, Irene, and his two daughters, Kate and Hannah.

Marcus Merriman, historian; born May 3, 1940, died March 23, 2006.