Glastonbury’s main stages are opening for the first day of the music festival.

Festival’s fans are hoping the weather does not dampen spirits.

Light rain is forecast for parts of the day, but festival goers may escape without the Somerset site turning too muddy.

Choreographer Michael Clark’s dance company will open the main Pyramid Stage.

The day will end with Florence and the Machine in the headline slot.

Florence Welch has replaced Foo Fighters, who pulled out when frontman Dave Grohl broke his leg.

The identity of the act that will fill the vacant slot before Florence has not been announced – and organizers hope to keep it secret until the performers step on stage.

However, organizer Emily Eavis did reveal that it is a band who have never played the Pyramid Stage and were not otherwise due to play at Glastonbury this year.

“There is definitely something filling that gap but under no circumstances will it be announced,” she said.

“Luckily it’s been a proper secret, a proper surprise, which actually is quite hard to do now because things get out.

“But there are only about four people other than the band that know about this. Even people that work on the festival don’t know about it.

“They’re coming because they want to play Glastonbury and they’ve never done it before on the Pyramid Stage. That’s all I’m saying.”

Friday’s acts include:

• Heavy rock legends Motorhead will make their Glastonbury debut on the Pyramid Stage
• Mark Ronson will bring special guests including Boy George and Daniel Merriweather to the Other Stage
• Russian punk band Pussy Riot will speak on stage about their opposition to President Vladimir Putin
• The Charlatans are the “special guests” who will open the Other Stage
• Scottish pop star Lulu will appear on the Avalon Stage

The decision to promote Florence and the Machine to headline status was criticized by some fans, but Emily Eavis said she made the decision “straight away” after Foo Fighters pulled out.

“This is her moment. She’s had a number one record in America, a number one record here, and she’s on fire.”

The choice of Saturday’s headliner also caused consternation.

More than 134,000 people signed a petition complaining about Kanye West’s appearance, and Emily Eavis even received death threats.

Emily Eavis said she did not take them seriously.

“In the Twitter world it’s very easy to think things are serious because you hear a voice quite loudly,” she said.

“But you realize it’s just one, and most people who come here are so open-minded and so up for it.

“I’m seeing a lot of Kanye T-shirts about. It was just an unfortunate amount of publicity for a petition from a guy who’d never been here before.”

Meanwhile, it has been confirmed that the Dalai Lama will make an appearance in the Green Fields on Sunday, June 28.

However, it is not clear whether Professor Stephen Hawking, who is due to appear in the Kidz Field, will attend the festival as planned.

Some 177,000 people are due on site during the weekend. Tickets, costing £225 ($360), sold out in 26 minutes last October.