Her time of 3:27:45 at the Isle of Wight Marathon was recognised by the International Association of Athletics Federations as a world best.

[1][nb 1] She was also the first woman to run two ultramarathons: the Isle of Man 40 in 1971 and the 55-mile London-to-Brighton race in 1972 – seven years before female competitors were officially allowed.

[4] Greig competed at track events, winning several medals at the Scottish Championships: Silver in the 880yds in 1956 and Bronze in the mile in 1958,1959, 1960 and 1966.

Greig held the world's best title until Mildred Sampson from New Zealand set a new mark nearly three months later.

[16] In 1974, at the age of 37, she won the first International Masters Marathon for women, at the World Veterans' Championships in Paris, with a time of 3:45:21.

[17] Greig's competitive running career came to an end in 1982, following an accident in a swimming pool in which she injured both her feet.

Along with Walter Ross, Greig was a member of the Organising Executive when the IGAL Veterans World Championships came to Glasgow in 1980.

The event was supported by the city council and was a huge success with hundreds of runners from 26 countries running in the 10k and marathon races.