A large cray fish or freshwater lobster has been found at Kenwood Ladies' Pond, leaving swimmers stunned.

The shellfish emerged last night from the swimming lake, to the amazement of lifeguards and swimmers alike.

Invasive crayfish species have increasingly become a concern to wildlife experts, as they can harm native pondlife in the Heath.

Gospel Oak resident Madeline Mussen had been waiting 50 minutes to swim in the sweltering heat at the popular wild swimming spot when the life guards were seen squealing about an intriguing object.

Pond regular Madeline said: “It was the size of my foot. This must have been some kind of jumbo cray fish.

“For the rest of my swim I thought I was going to be bitten by lobsters. It smelt like decaying leaves. It was really bothering the lifeguards.”

Cray fish, which are usually three inches in length, have been regular visitors to Hampstead’s ponds and have been known to nip swimmers.

The non-native species took over the ponds in 2012 with one fisherman reporting catching 180 of the creatures in one hour on the heath.

The same year the Ham&High reported there were suspicions a local Chinese restaurant had been fishing for the animals and serving them up to eat.

The creatures are known to sit at the bottom of Hampstead Heath’s bathing ponds and swimmers have even spotted herons eating the invasive animals.