Concerts, parades and thousands of street parties are being held across the U.K. to celebrate the royal's 60-year reign, and a host of British A-listers are joining in the festivities - even from sunny Hollywood.
Cowell says, "I'm holding a small private party for friends and family at my home in Los Angeles and will be getting up early to watch the festivities on television. I'm really looking forward to this. It's one of the great things about Britain. There's a lot to celebrate."
Brand admits he is upset not to be in London to mark the occasion as he is stuck Stateside gearing up to host the MTV Movie Awards in California on Sunday (03Jun12).
He insists, "It hurts my heart. It's a great time in our country and I'm devastated not to be there. I love the Queen and have never been so in love with her since I came to America. But we will be honouring the Queen in our own special way."
However, Caine, who was knighted by the Queen in 2000, is set to get a prime view of the action when Her Majesty takes part in a boating procession along the River Thames.
He says, "We're going to my flat in Chelsea harbour because that's where the Queen gets on her boat right outside my house. Genius. We'll be able to see her and wave her off. The Queen represents continuity, the passing of time, good health in older age and our great capital. I'm proud to be British."