The Queen and the Duke of Edinburgh watched a river pageant as they joined thousands of guests at a Diamond Jubilee garden party.
Arriving by passenger steamer for the party at Henley Business School, the royal couple were applauded by guests and wellwishers who gathered on the opposite banks to watch.
More than 30 vessels, including a Viking Boat crewed by University of Reading rowers, featured in the flotilla celebrating the history of the River Thames.
The Queen and Prince Philip travelled the short distance to the garden party from Hambleden Lock on board the Alaska, built in 1883 and the oldest working passenger steamer on the Thames.
The royal couple toured the garden party meeting some of the 4,000 guests drawn from the counties of Buckinghamshire, Berkshire and Oxfordshire, of whom 1,200 were chosen from an oversubscribed public ballot.
The Queen spoke to Simon Cruden, 31, from Oxford, who was accompanied by Sarah Clarke, 27, a Territorial Army volunteer from Southern Rifles headquarters in Reading.
Mr Cruden, who is registered blind as the result of a brain tumour, is due to carry the Olympic torch in Bicester next month.
"She said 'I have heard that the torch is quite heavy'. I said 'it may not look like it, but I have been practising'. She smiled at that which was very polite of her," he said.
The Queen, who wore a cream dress with a vine motif, a turquoise coat and matching hat, also met representatives from the community foundations for Berkshire, Buckinghamshire, Milton Keynes, and Oxfordshire. The foundations raise money to fund community and voluntary groups.
The Queen paused at the "communatree", where veteran broadcaster Sir Terry Wogan, who is a deputy lieutenant of Buckinghamshire, hung a message from one of its branches.
Sir Terry said the work of the foundations was "very important".
"There is a lot of poverty in all three counties and in my own, Buckinghamshire, in particular. What we are trying to do is to get people to come together and help locally."
The Queen unveiled a plaque specially made to commemorate her visit to the garden party, held at the Business School's Greenlands campus and hosted by the lord lieutenants of the three counties.
She was presented with a bunch of white roses by eight-year-old Alex Locke, from Marlow, Bucks, who underwent gene therapy at Great Ormond Street Hospital in London after being born without an immune system.
His parents, Colin and Carol Locke, said their son had at one stage been kept in an airlocked room because of his condition. They said it had been "absolutely fantastic" for him to meet the Queen.