Elephants leave zoo after dark

London Zoo's three female elephants are expected to move to their new home at Whipsnade this week in a cloak-and-dagger exercise worthy of a spy thriller.

A senior vet and two elephant house staff will lead the three animals into a converted lorry for the journey to Bedfordshire during the early hours of the morning, bringing to an end the zoo's 170-year association with elephants at the Regent's Park site.

Anxious that nothing goes wrong, staff have been busy rehearsing the move with the elephants every night for the past two weeks.

The zoo has kept the timing of the move secret fearing more bad publicity following the death of elephant keeper Jim Robson in October. However, sources at the zoo say a vet will visit the animals to ensure they are fit for the 90-minute journey to Whipsnade Wild Animal Park in Bedfordshire. If they show signs of stress the operation could be cancelled.

The three elephants will remain standing for the journey. As well as finding lying down uncomfortable, it also puts severe stress on their chest and lungs. Each animal will be confined in a separate crate similar to a horse box. There will be no restraints and the lorry will travel at a gentle speed to make sure the elephants are not knocked around.

Will Travers, director of the Born Free Foundation - which transports wild elephants in Africa - said the worst case scenario would be if one of the elephants collapsed during the trip.

"Getting them up from a prone position is not easy in such a confined space," he said. "You have no operating space to try and get them out. If the vehicle has a removable top then you could bring in a crane and drop a harness down through the roof and try and work around the animal. I just hope this doesn't happen."

The decision to move Dilberta, Mya and Layang-Layang to the more open Whipsnade zoo follows Mr Robson's death after he was crushed in his compound by one of his charges. An inquiry into the accident is under way.

Mr Travers said he hoped that there would be no need to anaesthetise the elephants - a last resort if they show signs of stress. "There is a small chance - about five to 10 per cent - that it won't recover from the jab," he said. "We help with a lot of elephant transportation in Kenya. Every time you knock out a big elephant there is always a risk that he will not wake up."

Dominic Tropeano, director at Colchester Zoo in Essex which has five African elephants, said the key to animal transportation was patience. "The trick is to take your time and be patient while encouraging the animals to relax," he said. "The keepers will talk to them and reassure them."