Hundreds of happy campers are waking up after spending a chilly night sleeping behind barricades in the streets surrounding Windsor Castle to grab the best spot for the royal wedding as 100,000 spectators are expected to watch this year’s biggest event on the British calendar.

As dawn broke over Queen Elizabeth’s Windsor Castle where Harry and Meghan will marry on Saturday at 9pm (Saturday morning local time), excited crowds began to assemble outside its ancient stone walls, home to 39 English monarchs since 1066.

With Union Flag camping chairs and Royal bunting in hand, the overnight revellers began filling up the pavements of Windsor as early as 7pm on Friday (10am on Friday local time) in a bid to secure the best vantage points.

Royal enthusiasts wrapped up warm to see out the night in the hope of catching a glimpse of the happy couple during the wedding of the year.

Millions around the world are expected to watch when Elizabeth’s popular grandson and the star of the TV drama Suits tie the knot at the 15th-century St George’s Chapel.

“I just think it will be magical. There will be so much shouting and cheering and noise. I love the royal family,” said Ronda Musgrove, 59, who camped overnight on the street opposite the castle to get the best view of events.

Tens of thousands of fans are expected to cram the narrow streets of Windsor, about 30km west of London. Security was tight and visitors had to pass through police search points set up around the castle.

A huge contingent of UK and international media – 5000 in total – have been accredited and are currently broadcasting from key locations around Windsor Castle.

The world’s media has been gripped by the union of Harry, 33, the sixth in line to the British throne, and Meghan, 36, a divorcee whose mother is African-American and father is white, and hundreds of TV crews have descended on Windsor.

Campers from France, Canada, the US and Australia have lined the streets of Windsor for a glimpse of Meghan and Harry. Photo: AAP

Nicky and Matt Pruner, from California, extended their holiday in the UK for an extra week so they could be in Windsor for the royal wedding.

Nicky Pruner, 62, said she had camped out all night at Kate and William’s wedding. “I said I would never do it again – and here I am.”

Matt Pruner, 63, said: “It feels like a festival, except this one has a meaning.

“It just gives hope to the world. We are very excited to be here.”

Travelling a more modest distance to set up an overnight camp in Windsor was Claire Aston, 74, from Ealing, west London.

She said: “I slept out three nights for William and Kate’s wedding and three nights for Charles and Diana’s.

“You would think I’m old enough to know better than to camp outside but rather stay at home in a comfy bed. But I’m a Londoner – we can do this sort of thing!”

Ms Aston, who managed to catch a glimpse of William and Harry earlier in the evening as they greeted crowds outside the Castle, said she was looking forward to the big day.

“It’s always a lovely crowd. You meet like-minded people with tales to tell,” she said.

After the ceremony, the newlyweds are expected to greet some of the 1200 members of the public invited into the castle grounds before setting off on a carriage procession through Windsor.

A reception will be held in the castle’s St George’s Hall before 200 guests join the couple at Frogmore House, another grand mansion on the grounds.

The prince and his new wife, who are expected to be given a new title by the queen to mark their marriage, are not immediately leaving on honeymoon and will carry out their first official engagement as husband and wife next week.