Photo gallery: Crowds turn the streets red, white and blue

Waving flags and clutching umbrellas against the predicted rain, the crowds waited with mounting excitement for the first glimpse of the couple - and in particular the bride’s dress, which has been kept a closely-guarded secret.

Kate was said to be nervous but calm as she made her final preparations for a ceremony that will be watched on television by two billion people worldwide.

The Dean of Westminster, the Very Rev Dr John Hall, who is conducting the service, told Sky News: “I think she will be quite calm, as a matter of fact.

“She seems to be very much in control of herself and looking forward very much to the day.

“After the final rehearsal when William and Catherine came on Wednesday evening, they both seemed to be very happy. I’m sure they will be a little bit nervous but I’m sure they can cope with that.”

Among the 1,900 guests invited to the Westminster Abbey service are a number of celebrities, including David and Victoria Beckham.

Victoria spoke of her delight at the occasion, writing on Twitter: “London looks beautiful!!! We are so proud to be British!”

Another of those attending the ceremony, TV presenter Ben Fogle, also expressed his excitement.

He wrote on Twitter: “Quick walk in Hyde Park with the dogs while the girls have their hair done. Very excited. London feels electric.”

As hundreds of thousands of well-wishers made their way to join the celebrations, a proud owner carried his British bulldog, draped in a Union flag, through Victoria station.

Burly men in crowns, women in glittering tiaras, children clutching flags and families with picnics all took to the Tube on their way to central London.

At Green Park station, the nearest to Buckingham Palace where William and Kate will kiss on the balcony later today, the platforms resembled rush hour as early as 6am.

Teacher Jackie Fowler, 28, from Putney, south London, and her friend Clare Gregory, 27 - who travelled from Leeds for the occasion - got up at 5am to make their way to the Mall to join in the celebrations.

“We’re so excited. I’m a massive royal fan anyway so this is just brilliant,” Miss Fowler said.

“We’ve dressed up like we’re going to a wedding, with our fascinators in. We’ve got champagne in our bag and we’re ready for a really great day.”

Miss Gregory added: “I’m originally from Northampton, which obviously has links to Diana, so as soon as it was announced I knew I’d have to be here to watch it live, not just on the TV.

“It’s a really great atmosphere, everyone’s so excited.”

Sisters Joan Fuller, 69, and Brenda Rowlands, 60, got up at 5am to secure their place in Parliament Square, which is part of the royal wedding route.

Mrs Fuller travelled from near Doncaster to her sister’s house in Woking, Surrey, yesterday.

“I walked the entire route as soon as I got here to have a look and see what was going on,” she said.

“I love the royal family and have sat on the Mall for many royal occasions, the last being the Queen’s jubilee.

“I am really looking forward to seeing William and Kate together and the atmosphere is amazing. There are thousands of visitors here, I just think it’s really good for the country.

“Diana would be very proud of William because she was so family orientated. William and Kate look so happy, I’m sure she would be delighted.”

On the Mall opposite Stable Yard, a group of students wore wedding dresses bought from charity shops as they joined the celebrations.

The famous Buckingham Palace balcony, where William and Kate will appear after the service for their first kiss in public, was decorated with a crimson drape lined with yellow edging.

There was a cheer from the crowd as palace staff began preparing the balcony for the historic kiss.

At London’s Heathrow Airport, the national anthem was played as passengers awaited their flights this morning.

The crowd employed their Union flags for a wide variety of purposes - as well as waving them furiously, they wore them as scarves and draped them around their shoulders against the early morning chill.

The royal wedding has captured the imagination of the American public, and the stars and stripes was also in evidence outside the abbey.

Many of those who travelled to London for the occasion made special efforts, with young girls sporting princess outfits and one man wearing a fake crown and sunglasses.

Kingsley Glover, a fellow pupil of Miss Middleton’s from her days at St Andrews school in Pangbourne, near Reading, was in Bucklebury to celebrate the big day.

He told ITV’s Daybreak: “She was quite quiet, she was good at sports, she was in the hockey team, the swimming team as well.

“I was in a few plays with her at school, we were in the choir as well.”

Mr Glover played alongside Miss Middleton in the Victorian melodrama Murder In The Red Barn, when he played the role of William.

Footage of the play, when Miss Middleton was 13, has been posted on YouTube.

Mr Glover said when the royal bride first rose to fame, he had no idea she was the same person he had gone to school with.

“I had no idea that Kate Middleton meant Catherine Middleton who I went to school with.

“Someone said, ‘Didn’t Catherine do well?’, and I said, ‘What’s she doing now?’.”