A Morden secondary school was locked down and pupils kept indoors following false reports of a gunman on the loose in Seddon Road this afternoon.

Police labeled the 999 caller’s claims as a hoax after an armed unit rushed to the residential address and investigated.

More than 1,000 students were held in Bishopsford School for over an hour with some parents left stranded outside the gates until officers gave the all clear.

But the school’s principal Andrew Barker said: ”My jurisdiction was to ensure the safety of the staff and pupils at the school.

"It would take just one child to get caught in the cross fire and we weren’t going to let anyone out until given the green light by police.

"The children were completely co-operative and behaved brilliantly after I told them over the tannoy that they were being kept behind."

Parents were informed by text message that the school was secured “due to a police incident” and students were help in their last lesson until 4pm, an hour and a quarter after the alarm was raised.

Mr Barker added: "We have a pre-prepared plan in the case of an emergency and I’m really pleased with the way things went.

"I’ll have a meeting with staff before we get on with the rest of the school’s work for the evening. Tomorrow’s a new day."

A police spokesman said: "We received a phone call from a member of public who thought they’d seen someone going into an address in Seddon Road with a firearm.

"A report of this nature can only be responded to by armed police. It looks like someone thought it would be funny to waste police time in this way."