The biggest Glastonbury Festival ever was in full swing this lunchtime as almost 150,000 music fans braved torrential early morning rain and increasingly muddy conditions.

Eclectic Laplanders Adjagas opened the Pyramid stage, before the sun came out for a storming midday set from Dundonian rockers The View, described by one reveler as “like the Crazy Frog singing indie punk.”

Festival organiser Michael Eavis has spent £750,000 ensuring this year’s festival avoids the muddy mayhem of previous years.

But already main paths, campgrounds and walkways are muddy underfoot and foolish Antipodeans in flip-flops are regretting their footwear choices.

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Mr Eavis, who this month received a CBE at Buckingham Palace, invested in new flood defence barriers and engineering works following the storms of 2005, when 300 tents were washed away.

The works installed on site include bypass channels to increase water flow capacity, built by the Environment Agency, and hundreds of metres of new drainage pipes.

Mr Eavis said: "We have had a lot of work done to the site and are fully prepared. There are so many more covered stages and if we get the occasional shower - we are used to it."

Record numbers had arrived at the Somerset venue by this morning, apparently determined not to let the weather ruin their fun. Police said 148,500 revelers and staff had arrived, with 12 people arrested attempting to jump the fence.

Most festival-goers came prepared for the worst, wearing climbing boots or heavy-duty wellingtons, waterproof jackets, trousers and warm jumpers.

But many have still failed to heed the weather forecasts, with reports that wellies are now selling for £80 outside the site, even though outdoor equipment shops inside the festival compound still have many pairs available for £20.

Police predicted that roads in to the festival site are expected to be clogged up for miles as 30,000 more people rush to Glastonbury before Friday night headliners Arctic Monkeys take to the Pyramid stage this evening. Amy Winehouse, Kasabian and The Fratellis are also likely to draw huge crowds on the opening day.

The festival, which is the largest greenfield event in the world, covers 900 acres in the Vale of Avalon, which local legend has it is the site where King Arthur was buried.

More than 700 acts will perform on 80 different stages over the three days.

Organisers hope a green campaign encouraging festival-goers to be environmentally-friendly will cut the volume of waste by 50 per cent compared with 2005.

With security significantly stepped up on previous years, police this morning said that only 13 thefts from tents had been reported.

After this morning’s deluge, forecasters said showers will remain relatively limited today, but the weather will be changeable all weekend.

Michael Dukes, MeteoGroup UK forecast manager, said: "Heavy downpours will never be far away throughout the next three days. It may start clearing up by Sunday evening."

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