It is reported that Duff hosted Al Maktoum several times in Scotland at Gleneagles Hotel, during the latter's visits to the place. The relationship is also cited as the reason behind the donation of 1.16 million the erstwhile Dubai ruler made to the Exeter University for its library and later, for the Institute for Arab and Islamic Studies. After the death of Sheikh Rashid in 1990, Duff slowly withdrew from the Dubai administration and restricted himself to his role as an Honorary Advisor to the Ruler. He continued his life in Dubai where his wife, Irenka, managed the Dubai English Speaking School, the school he founded, till a few years before Duff's death. He died in his sleep on 14 February 2014 at his villa along the Jumeirah Beach, leaving Eleanor, his wife, Diana Barnardiston and Sheila Duff-Earles, his two daughters and four grandchildren, Michael, Andrew, Nicholas and Caroline. His mortal remains were laid to rest at the nearby Christian Cemetery in Jumeirah, the one he had helped establish.