Heavy overnight rain, which needed North Yorkshire Fire and Rescue Service to pump water out of the pig lines at 2am, left conditions difficult underfoot.

Minutes before the Royal couple arrived at the 150th show, officials decided that carpet was needed to cover muddy patches on the President's Lawn.

Interlocking squares of rubber matting were brought in. One side was black. The other side was red. But it was the black side which faced upwards.

Despite the threat of more rain, a large crowd greeted the couple when they arrived to be welcomed by the President of the Yorkshire Agricultural Society, Christopher Hall, of Eavestone, near Ripon, and the Honorary Show Director, Bill Cowling, who farms at Pannal, near Harrogate. Even before she reached the showground, the Queen knew that she had enjoyed a successful Great Yorkshire Show.

She told Mr Cowling that her Bay gelding, Petition, had won the Large Riding Class – a qualifier for the Horse of the Year Show.

Before beginning her showground tour she met staff involved in staging the £2m event, and was shown a photographic display depicting 150 years of the Yorkshire Agricultural Society.

She was also presented with a copy of the commemorative book Great Yorkshire – A Celebration of 150 Shows, edited by David Joy, and a hamper of locally-produced fare. The Duke was given a Yorkshire Agricultural Society tie.

Undeterred by sticky conditions underfoot, the Queen who wore a royal blue coat with a matching hat trimmed with a pink ribbon, ignored the Wellington boots favoured by some of her escorts and remained loyal to a pair of smart black shoes.

Highland cattle breeder Anne Barugh, 83, of Bridlington, who sold the Queen a bull 25 years ago, met her as she toured the cattle ring. Miss Barugh said: "The Queen wanted to know how we had done." Her stockman, Eric Robson, told the Queen they had won the female championship with Bachy Mor of Easton.

Patrick Tolan, of Pudsey, whose 120-year-old Norfolk carriage was pulled by his pony, Rosegarth Crusader, should have been competing in the Private Driving Classes, but conditions meant they were cancelled. Mr Tolan, who revealed that the Queen had expressed her sympathy, said: "She asked me how long it had taken to clean the carriage and I told her it was about a week. Now it will take another week to clean again."

The Queen, whose grandfather King George V was a Cleveland Bay enthusiast, still has 35 pure and half bred horses in the Royal Mews at Hampton Court, where her stallion Mulgrave Supreme has influenced the breed over 45 years.

She spent a long time in the Ridings Ring discussing a display by the Cleveland Bay Horse Society, which celebrates its 125th anniversary next year. James Stephenson pointed out to her Ludon Principal, a stallion owned by Lincoln University, which covered one of the Queen's mares earlier this year. The mare is now in foal.

A £5.1m Regional Agricultural Centre, which the society is building to showcase the best of the region's produce, is still at the foundations stage, but the Queen unveiled a commemorative plaque set in a dry stone wall. They will be moved to become part of the finished building when it opens in May, 2009.

After lunch, which included Bleiker's smoked salmon from Nidderdale and sirloin of beef supplied by Cliff Hollins Farm at Oakenshaw, Bradford, the Queen and Duke joined a packed grandstand to watch the Champions' Cattle Parade.

Before she left, the Queen was presented with a posy of white roses from Emily Wilkinson, four, daughter of the Yorkshire Agricultural Society's facilities manager, Sarah Ferguson, who had watched as the heavy rain spoiled her carefully prepared showground.

The Queen sympathised, saying: "You must have had a terrible time with the weather?" Miss Ferguson replied: "We have had a terrible couple of days, but it has all been worthwhile today."