A novel rescue by 50 emergency staff and marine specialists has saved a stranded whale and seen it safely out to sea.

Firefighters dug a trench in mudflats on the Humber estuary and then worked with other specialists to turn the 15-tonne minke whale round and gently heave it loose.

Boats were used alongside the rescuers to create wakes that helped the 30ft (9 metre) mammal's escap e after eight hours on the edge of Immingham, one of the UK's largest docks.

The alarm was raised when the stranding was spotted by a passing ship at 8am on Tuesday, an estimated four hours after it is thought to have grounded. A second, larger whale was seen circling nearby and rescuers believe that ship movements may have confused the younger one.

Torrential rain also eased the animal's plight although it stretched the rescue team and monitors who are now stationed round Immingham in case the minke turns back inshore. This has happened previously with disorientated whales and the RSPCA said the minke had initially tried to resist the turn-round effort.

A witness of the operation, a 58-year-old local man who did not wish to be named, said: "The teams waited until high tide but that was still quite low so there wasn't enough water. They turned the whale to face the sea but it kept wanting to come back in.

"To make the water deeper, they had boats running up and down alongside the whale to make a wave so the water was high enough to get it out. They then basically walked it out towards sea and then it just swam out. Hopefully, it will able to make its way down the Humber now."

Geoff Edmond, of the RSPCA, said: "We got on the scene this morning when coastguard and RNLI crews were already in attendance with a vet. We waited until about 1.30pm when it was high tide to attempt to re-float the whale.

"With a lot of effort and advice from the vet everyone managed to re-float it. It hung about for a bit before finally disappearing from view. It still needs to get back into the North Sea so I think the next 24 hours will be crucial."

Earlier Mike Puplett, of Humber coastguard, said low tide had hampered initial approaches and raised concern that the whale might be crushed by its own weight as water levels sank to cover only some 10% of its bulk. But rescuers were heartened by continuing signs of life as the tide came back in.

Minkes prefer the open sea but are occasionally drawn close to land where they become vulnerable to unfamiliar tidal movements.