Walkers are being warned about the dangers of tides after a group of stranded teenagers had to be rescued.

The party of five boys was half-an-hour from being engulfed by the sea at the foot of Beachy Head, said Eastbourne Lifeboat coxswain Mark Sawyer.

They were supposed to be walking along the clifftop from Birling Gap to Eastbourne as part of a school trip.

But the group of four 17-year-olds and one 16-year-old took the wrong route and found themselves on the beach below with the tide racing in.

Their mobile phones had no signal so they waded into the sea and scrambled on to the base of Beachy Head lighthouse to find a higher vantage point.

A member of the public saw them waving and in distress and called the emergency services at about 5pm on Friday.

Mr Sawyer said: "Sometimes people do not realise how dangerous it can be to go walking at the foot of these cliffs without having studied the tides and being fully prepared.

"These young people were unaware they were walking into a potentially lethal situation. They had no more than half-an-hour before they were in serious trouble.

"It may look safe but the tide can come in very fast and leave you stranded very quickly. There is no way up that cliff face.

"People discover that mobile phones just do not work from there so they cannot raise an alarm."

The all-weather boat and inshore lifeboat were sent to the scene.

Mr Sawyer said: "They were wet and cold, tired, fed up and pretty scared but otherwise unharmed but they were very fortunate to be seen by the vigilant person at the top.

"We took them back to the beach at Eastbourne and contacted their teacher and gave them all a bit of a talking-to about safety."

Mr Sawyer said anyone attempting a similar walk must check the tides and ensure they have enough time to complete their trek.

He said: "It's probably best to do it with someone experienced and not a good idea for unaccompanied children.

"It's rough terrain and quite a gruelling walk. You must have warm clothing because the weather can draw in very suddenly and they should also have plenty to eat and drink.

"It's a good idea to have somebody at home who knows what time to expect you so they can contact us if you are late."