The bitterly-disappointed chairman of Wayland Agricultural Show warned today that its enforced 11th-hour cancellation because of a sewage spill could put in jeopardy the whole future of one of Norfolk's best-loved and historic countryside spectaculars.

Organisers of the 139th show, which had been all set to open at Watton this morning, called off the whole event last evening after raw sewage flowed on to the showground site when lightning put a nearby Anglian Water pumping station out of action.

Exhibitors, stallholders and farming families drawn from far and wide had been making the final preparations to welcome hordes of showgoers when disaster struck. Last year's attendance of 15,000 was a record, and the show team was expecting to match or even top that figure today at what is one of the oldest one-day agricultural shows in Britain.

Show committee chairman Graham Shingfield said the extent of the leakage was discovered only at about 6.15pm yesterday and the decision to cancel the 2012 show was taken shortly afterwards.

He added: 'I am devastated - absolutely devastated. It is soul-destroying, to be honest, that we have had to do this through absolutely no fault of our own.

'It is going to cost us thousands and thousands and thousands of pounds - it could break our show. We cannot insure against risks like this.'

And he added: 'There is no way we will be able to give any money away to local charities this year. That is always something we have endeavoured to do because it is part of our remit.'

Mr Shingfield, of Manson Green Farm, near Hingham, said the crisis emerged when the show organising team and some of the 40-plus band of volunteer helpers realised the gateways to the Brandon Road showground were getting very wet.

'Then someone said: 'Look where it is coming from.' The stuff was going in the ditches and it was getting everywhere,' he added. 'It was like a river.'

Mr Shingfield said the water company had an engineer on site quite quickly but the effluent had contaminated about an acre and there was no alternative but to call off the show.

This morning, organisers and exhibitors faced a logistical nightmare trying to clear the showground of marquees, animal pens and stands without risk to their health. Mr Shingfield said they had cordoned off the affected land and were using a second entrance to remove vehicles and equipment. Hand gel was being made available to help avoid the risk of infection from the sewage.

Asked if Wayland Show would seek compensation from Anglian Water, he said: 'We shall have dialogue with them - we want to talk to them. But we are very cross.'

He said one showgoer he had spoken to this morning had driven down overnight from Blackpool, only to discover the event was off.

Lots of families planning to visit the show to see the livestock and equestrian events, cookery and lifestyle displays and grand ring attractions had booked online. Asking people to check out the website www.waylandshow.com in the days ahead, Mr Shingfield said today: 'We shall endeavour to refund people as soon as possible.'

Anglian Water spokeswoman Carly Millership said an electrical storm tripped out the pumping station, putting it out of action for about an hour and a quarter.

The downpour, plus the build-up of effluent from the station, had contributed to the leakage. Most of the outflowing sewage ended up in ditches adjoining the AW installation and showground.

She said an Anglian Water engineer and team were on the scene from about 7.45pm yesterday, pumping out and removing the effluent by tanker. They completed the operation shortly after midnight.

Ms Millership apologised for the problems the spillage had caused but said unduly bad weather such as the electric storm that had affected Watton yesterday afternoon could create problems. She added: 'All we can do is make sure, as we did last night, that we are on site as quickly as possible to resolve the issue.'

Of the prospect of compensating Wayland Show, she said: 'From our point of view it is too early to take that decision. We shall obviously be having discussions with the event organisers.'

Ms Millership said there had been no threat of contamination to local water supplies nor to the Cranswick food processing plant near the showground.

Mr Shingfield said: 'Next year was going to be our 140th year and we were going to have a celebration. Hopefully, we still will be able to. But obviously for now we are just upset and annoyed.'

The 2012 Wayland Show had been a year in the making: preparations for each event start almost as soon as the previous one has ended. The show draws livestock entrants and judges from all over the country, and there had been high hopes that this year's event would yield a charity cash pot of more than �30,000 to distribute to good causes.