Figures gathered from register offices around the country suggest that most of the couples taking advantage of the civil partnership law are male with at least one of the pair being over 50.

They want to ensure that their long-term partners benefit from the new law, which gives them pension and inheritance rights equal to those of married couples.

Elton John, 58, says such rights are one of the main reasons he and David Furnish, 43, are undergoing the ceremony. “We’ve been together for 12 years and we’re able to do it, so why not,” he said last month. “It gives us protection. If one of us dies, it protects the other person.”

Under the new law, a partner can inherit all their property tax-free. They also keep the same proportion of the other’s pension income as if they had been widowed.

Figures gathered last week from Brighton and Hove, Westminster, Islington, and Kensington and Chelsea, the councils conducting the largest number of civil partnership ceremonies, show that more than 54% of all the 381 planned unions involve men over 50.

The rest are largely between younger men: 52 couples are female.

A broader study of 12 London boroughs, towns and cities found that 32% of people planning civil partnerships were women.

Ben Summerskill, chief executive of Stonewall, the homosexual rights group, said: “There is a backlog of people who have been in long-term stable relationships who want to benefit from a civil partnership.

“When you have been together 30, 40 or even 50 years you are reasonably certain about tying the knot, unlike people like Britney Spears who got married then had the marriage annulled just days later.”

Among those taking part in the ceremonies will be Angela Mason, director of the government’s women and equality unit, who will register with Elizabeth Wilson, her girlfriend of 30 years.

Mason, 61, believes years of discrimination against lesbians still deter large numbers from making their relationships public. She said: “Lesbians have traditionally been doubly oppressed, first as women and secondly for their sexuality.

“Things are improving today but there is still a hangover from the earlier period of sexual oppression and I think many simply haven’t come out. Perhaps it will change in years to come.”

Most attention will be focused on Elton John’s nuptials. The registration ceremony at Windsor Guildhall, where the Prince of Wales and the Duchess of Cornwall were married in April, will be a modest event for family only.

The £1m reception in a marquee at John’s nearby mansion, by contrast, will be a flamboyant affair. Caseloads of vintage pink champagne have been ordered, while the 700 guests include celebrities such as Elizabeth Hurley, Victoria Beckham, Lulu, Sharon Osbourne and Donatella Versace.

John will not be expecting any gifts, but he has asked for donations to the Elton John Aids Foundation.

The honeymoon remains a closely guarded secret, with Furnish reportedly determined to keep the new year trip as a surprise for his partner.

The couple will not be the first to tie the knot. That distinction will go to civil partners in Northern Ireland, where the first ceremonies will take place tomorrow, one day before those in Scotland and two days before England and Wales.

A total of 687 couples are scheduled to enter into civil partnerships on Wednesday.

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