• The Duke of Hamilton at Lennoxlove House on the family estate in East Lothian Picture: Susan Burrell
Angus Douglas-Hamilton, the 15th Duke of Hamilton, died in his wife's arms in his home in the early hours of Saturday.
The duke, who was diagnosed with dementia in 2001, had become increasingly ill over the past two months. He was 71.
His wife, Kay Hamilton, a passionate animal rights campaigner, last night paid tribute to her husband as a "wonderful, fun and loving man".
She spoke of how they had shared their last night together in their East Lothian home. "Over the last few days he had become increasingly ill and we knew that time was running out," she said. "He died peacefully in the early hours of Saturday morning in my arms in the comfort of our home."
The duke was hereditary bearer of the Crown of Scotland to the Parliament of Scotland, so had the honour of carrying the Crown in front of the Queen at the opening ceremony of the Scottish Parliament. The duchess last night recalled the moment he nearly dropped it.
"He was walking with the crown on a cushion and as he came down some steps he almost lost his footing and was about to shout out to his friend the Lord Lyon, 'Here, catch', but he swallowed his words when he realised the Queen was right behind him."
In his younger days the duke was a keen flyer and car-racer.
Both the duke and duchess have been active animal rights campaigners over the years, banning hunting on their Lennoxlove estate in East Lothian and boycotting Edinburgh department store Jenners until it stopped selling pat de foie gras. They also had a passion for Staffordshire terriers.
The duchess said last night she would continue their work. "I will carry on with the animal rights work that we were both so passionate about," she said.
In a tribute to her husband, she also said she would continue her long-running campaign for people with dementia to be treated by specialist nurses in hospitals.
She added: "Even though the dementia made things difficult we still had fun together."
The heir to the Hamilton titles is their eldest son, Alexander Douglas Hamilton, Marquess of Douglas and Clydesdale, who was born in 1978.
The duchess added: "My husband supported many worthy causes and I know he was content that his son Alex as the new duke will be able to carry on and expand these activities."
A spokesman for Buckingham Palace said: "The Queen is sending a personal message of sympathy to the family."
A private funeral for friends and family will be held this week and a memorial service is being planned for later in the summer.