The veteran Nationalist campaigner said yesterday: "I was married to Margo for 33 years and I will remain married to her until the day I die. I can't describe the loss. It's enormous."
Ms MacDonald, who died on April 4 had been diagnosed with Parkinson's Disease in the mid-1990s and was told at the end of January that she had about three months to live after being admitted to hospital for three weeks on Christmas Day battling with the effects of lymphoedema - a chronic condition that can lead to breathing difficulties among other side effects.
Mr Sillars revealed she spent her final weeks tying up loose ends at home and buying clothes from TV shopping channels.
"She'd try to pass her time on QVC while other moments were spent preparing for her death. She couldn't settle until she'd allocated her rings to her granddaughters. "She picked a specific one for each, dependent on their different personalities."
Mr Sillars also revealed that his wife had organised redecoration of the house.
Delivering the eulogy to his wife last week had been difficult, he said. But he was keen to try to sum up "the essence of Margo" adding she had a "very strong" relationship with the public.