Lucas and long-term boyfriend Kevin McGee's partnership ceremony was followed by a lavish pantomime-themed reception at a 17th-century palace in December 2006.
Today they said their split was "amicable".
A joint statement from legal representatives Mishcon de Reya and Withers LLP said: "It is with sadness that Matt and Kevin announce that their relationship has come to an end.
"Their separation is amicable.
"They ask the press to respect their privacy at this time and to exercise restraint in any reporting of this matter."
The pair had been together for three years and were engaged for seven months before their civil ceremony.
Their service took place at Home House, a private members' club in London, and both wore suits.
But the reception, at Banqueting House in Whitehall, was one of the biggest showbiz events of the year.
Lucas, 34, dressed up as Aladdin and TV producer McGee went as Prince Charming.
Guests included Sir Elton John, as Captain Hook, and Courtney Love, as the Queen of Hearts.
Lucas's Little Britain comedy partner David Walliams, who was not best man, attended as a spoof Christopher Biggins.
Other guests included comedian Paul O'Grady, EastEnders actor Steve McFadden and actress Barbara Windsor, as the Fairy Godmother.