Peter said: “Politically, it’s hugely significant to us.
“It’s our government – and society – recognising gay relationships as equal.”
It is also important personally for the 49-year-old.
Peter, who is a campaigner and writer from Lanarkshire, and David, 42, who works in finance, have been together for 17 years and have two children they adopted six years ago.
For him, the marriage is an important marker in their long relationship and a chance for a celebration with around 100 friends and family.
It is also a chance to redefine marriage and take it out of the hands of Tories and traditionalists.
He said: “I’m not buying in to a conventional marriage and I don’t want people to think that’s what this is about. We are changing marriage – it is not marriage changing us.”