The dead body of a 12 stone porpoise was found dumped in an alleyway - more than a mile from the coast.

Mystery surrounds how the 4ft long mammal got to Tarring, just outside Worthing in Sussex, as they are banned from being kept as pets and rarely in captivity because they have difficulty adapting.

The animal was found lying in its own blood on Saturday evening by passersby and experts believe its appearance in the alleyway was probably the result of a 'strange Halloween prank.'

The porpoise is believed to have died after being washed up on the beach and had been dead for around two days.

A porpoise was found in an alleyway in Tarring in West Sussex, more than a mile from the shore, on Saturday

The porpoise, weighing 12 stone, had to be covered with biohazard bags before it could be collected for testing

Tim Allen, 31, was told the animal had been found on Saturday evening.

He said: 'It was all so surreal. How on earth did a dead dolphin end up in our alley?

'It looked like it had been dragged, but even so, that would require a lot of effort.

'We're all floundering as to who, or what, would do such a thing. It's mad.'

The animal is a male harbour porpoise, which usually travel round in small groups and are traditionally hard to spot as they rarely come out of the water. From a distance they look similar to dolphins and are often found in the North Pacific, North Atlantic and Black Sea.

Tarring, in West Sussex, lies around 1.2 miles from the seafront.

The RSPCA has since received reports from people saying they saw the porpoise washed up on the beach.

Mr Allen added: 'Nobody has a clue how it got here. We were all stood round, all bemused. One old lady reckons it was dumped there as part of a revenge attack straight out of the Godfather.

'I'm not so sure - unless you live on our estate, you wouldn't have any reason to even know that that alley exists.

'There was a little girl who saw it and looked really upset. If it was put there as a joke, it wasn't a funny joke.

'It's not a through path to anywhere but our homes. It's all so strange - if it was a cow, at least it could have got there and died on its own.'

Mr Allen rang the RSPCA who sent an inspector round to examine the porpoise. They then covered the animal in yellow biohazard bags until it could be picked up on Sunday.

A spokeswoman from the British Divers Marine Life Rescue programme, which helped remove the animal, said it had probably died after becoming stranded on the shore.

Porpoises are banned from being kept as pets in the UK and there are no known cases of them being kept illegally, as they are very difficult to house and would need huge facilities like dolphins.

The porpoise was found in Tarring in West Sussex on Saturday night - which is more than 1 mile from the sea

The dead porpoise was found dumped in the Sussex alleyway on Saturday by passerby in Tarring, Sussex

She said: 'It had been dead for a day or two, and we are putting this down to some kind of prank. It was Halloween.

'You have to bear in mind it was a 4ft animal, so probably a couple of people carried it, realised they couldn't do anything with it and dumped it. The animal had been dead two days and was decomposing badly. It was not going to be particularly pleasant and would have been pretty smelly.

'Generally most people would never have picked it up, and someone out there is likely to have some very smelly clothes.'

The corpse has been taken to the Zoological Society of London, where a post-mortem will be conducted by the Cetacean Strandings Investigation Programme - experts in all large marine animals who are found washed up on our shores.

A spokesman from the RSPCA said: 'It is at present unclear how the animal died but it is hoped tests will provide answers to this.

'He may have died from natural causes and washed up on the beach, and then later transported inland.