Meghan Markle's father, Thomas Markle, has become a heading for the royals ahead of Prince Harry's wedding

The drama surrounding Meghan Markle's father has overshadowed the build-up to the big day.
The drama surrounding Meghan Markle's father has overshadowed the build-up to the big day.

Meghan Markle's father has overshadowed his daughter's wedding to Prince Harry by sowing confusion about whether he would walk her down the aisle or snub the British royal family by pulling out of the intricately planned celebration at the last minute.

As royal fans convened on the genteel English town of Windsor where Harry is due to wed the American actress on Saturday, the role of her father, Thomas Markle, was still unclear after he issued a flurry of statements to an American news website.

On Monday, he was reported by the Los Angeles-based celebrity website TMZ.com to be unable to attend due to a heart attack and embarrassment over whether he had staged pictures with a paparazzi photographer. But the same website said on Tuesday he had changed his mind and would go to be part of history.

TMZ later quoted him as saying the trip was off because he needed immediate heart surgery.

Markle, who lives in Mexico, had been due to walk his daughter down the aisle on Saturday at St George's Chapel in Windsor Castle in front of 600 guests, including all the senior British royals and a smattering of celebrities.

Britain's Sun newspaper, the country's best selling, had to scramble to update its front page to reflect what it called the "Royal Sensation" of Thomas Markle's absence under the headline: "I've got heart op today". It offered four pages of analysis.

"It must be really upsetting but I'm sure her mum will do a fine job," Scott told Reuters.

On Windsor's streets, hundreds of tourists and journalists mingled with dedicated royals fans - some draped with UK flags and holding photographs of Harry and Markle while armed police patrolled.

Some fans are sleeping out on the street until the wedding, seeking to secure the best positions to see the couple.

"I want them to come through those gates. I want them to look at me, wave and smile," Donna Werner, who flew 4800km from New Fairfield, Connecticut, to be in Windsor told Reuters.

"That will make it all worthwhile. It really will," said Werner, 66, camped outside the castle, dressed head to toe in a mix of British and US flag-themed attire, including a shirt that read "Prince Harry, I'm still available. Last chance!"

Windsor, which is dominated by the royal castle, was decorated with swathes of red, white and blue Union Jack flags. Stalls sold Harry and Meghan scarves for GBP15 ($A27) and commemorative caps for GBP10.

More than 100,000 people are expected to descend on the town on Saturday. They will have to clear airport-style security before being allowed near the main venue, said Superintendent Jim Weems, the police's tactical commander for the day.

Britain is on its second-highest threat level of severe, meaning an attack by militants is considered highly likely. Last year 36 people died in four attacks. Despite the tight security, Weems said there was no particular threat against the wedding.

"There's no intelligence to support that this event is going to be particularly targeted," he told Reuters.

Australian Associated Press