Fantasy-style lily pads

As playpens go, it offers a few natural advantages - it's nice and soft underfoot, there's plenty of room to crawl about, and woe betide anyone who strays out of bounds.

Despite the signs that summer is perhaps finally here, these giant water lilies are unlikely to catch on as the latest garden playtime accessory this year.

The massive specimens, measuring more than six feet in diameter, occupy pride of place in the Water Lily House at London's Kew Gardens, which celebrates its 150th anniversary this year.

Thanks to the unique conditions generated inside - the water is heated to a constant 27C - the house can recreate the atmosphere of the South American river deltas from where intrepid Victorian botanists first took the plants.

Kew's botanists say the lilies are so strong that they will hold a small child - a claim the Evening Standard put to the test.

And so it was that young volunteer Byron Evans, aged one and weighing 1st 9lb, found himself enjoying an unexpected stint as a spot of novelty pond life.

His mother Diane, 30, from Balham, said: "We were a bit nervous about what would happen - the lilies don't look as if they'd take much weight.

"It dipped down a bit when you first put his weight on it, and some water seeped through the bottom of the plant itself. But it still held him up."

The first live specimens of Victoria cruziana, native to Paraguay and Bolivia, were brought to the UK by Sir William Hooker, the first director of Royal Botanic Gardens, in 1849. He managed to keep the seeds alive by transporting them across the Atlantic in phials of pure water.

The seeds produced three plants, one of which was given to Kew, another to the Duke of Northumberland at Syon House, across the river from Kew Gardens, and a third to the Duke of Devonshire, at Chatsworth House.

Despite being only one millimetre thick, the delicate veins and ribs on the pad's underside trap myriad pockets of air, enabling it to support substantial weights.

So effective is the design that it helped inspire the blueprint for the steel-and-glass structure of Crystal Palace, built in 1851.