Kate Middleton looked resplendent as she walked down the aisle on Prince William's arm. The only hitch - the wedding they were attending wasn't theirs.

Instead, the couple were watching guards officer Nick van Cutsem tie the knot, and he said to them, ‘You're next!'

But whether William and Kate really will be the next to marry has become a contentious issue.

The royals are grappling with the problem that Princess Anne's daughter Zara Phillips is keen to announce her engagement to rugby champion Mike Tindall, after dating for six years.

‘I don't think it's about if we'll get married but when,' Mike says.

But the Queen is unlikely to give her seal of approval to two royal weddings at the same time - and both couples want her OK. Now Kate's determined to beat Zara with an engagement announcement and a wedding.

‘The race is on and it's causing a lot of conflict,' a royal insider says. ‘While Kate is determined not to let anyone steal her thunder, Zara's furious she's being forced to plan her life around what Kate and William may or may not do.

‘But Zara is royal and there are protocols. There's the question of when William and Kate will make an announcement. And there can't be two at once.'

The girls have been pipped at the post by Lord Freddie Windsor, who will wed actress Sophie Winkleman next month, but both want to be the next royal bride.

Zara, 28, and Mike, 30, recently bought a $1.6 million home in Cheltenham, fuelling rumours they're ready to marry. And they have spoken openly about kids.

‘I'd like to have children one day, but it's about finding the right time,' Mike says. ‘I'm quite a traditional guy so I think I'll be doing it the usual way round - marriage first and then children.'

But Zara and Mike may have to put their plans on hold for another few years. William and Kate are expected to get the Queen's approval to marry when they meet with her at Balmoral this week. And it looks like the wedding won't be for some time - the pair have ‘struck a deal' to marry in 2011.

The right time

As part of a secret pact, Kate, 27, and William have formulated a plan that will ensure they're married by the time the Queen celebrates her historic Diamond Jubilee in 2012.

In the meantime, palace sources say 27-year-old William and his advisors, including his father Prince Charles, have devised a scheme that will raise his profile as the future king.

A royal source tells the UK's News Of The World, ‘The timing is important. It would be wrong to force the situation before William is established in his own right.'

The palace fears William's identity will be lost in the frenzy of an engagement announcement, in the same way Charles' profile crumbled when he wed Diana. They're desperate to avoid a repeat of ‘Di-mania', fearing Kate could turn into a superstar before William establishes his identity.

The profile of Prince Harry will be raised too - effectively promoting the pair as a ‘winning double act'. This suggests that even after they wed, Kate will take a low-key role. The royal insider says, ‘It's hoped Kate will play a supporting role, as the Duchess of Cornwall has for the Prince of Wales.'

But the plan's almost certain to fail. As the the UK paper says, ‘This is wishful thinking. Everyone knows that, once out of the bag, the marriage story will have legs of its own. It will run and run.'

By Christine Spiteri

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