Some 40 children at Highfield Nursery in Ipswich got well and truly filthy yesterday to celebrate World Mud Day.

The children, between three and four, dived into nearly 200 litres of mud with a splatter, coating themselves in dirt with reckless abandon.

The initiative, held for the first time, was designed to demonstrate the health benefits of playing in the dirt and connecting with nature.

According to Ruth Coleman, who works at the nursery, scientific research has shown that playing in mud releases serotonin into the brain.

She said: “This is the first time we have done Mud Day and it’s been a lot of fun. This is probably the only real opportunity that children have to get really, really muddy. We are giving them their time to play without boundaries. They will probably remember this day when they’re 16.”

Altogether 80 litres of compost and over 100 litres of top soil were used to make the mud, which was mixed with water over a plastic sheet in the nursery’s garden.

Kate Dodd’s daughter was one of those who took part. “She’s had so much fun. It’s all in her hair, in her ears, all where you would expect it to be.”

Ruth said the parents reacted surprisingly well to the idea.

“They were a bit aghast at first, but we were pleased that we decided to do it here so they didn’t have to get muddy at home.”

She added: “We firmly believe in the value of risky freedom and risky play. We always look at risk versus benefit, and if the benefits outweigh the risk we go ahead and do it.”