One of the world's deadliest snakes is loose in London (and it's faster than a horse)

London is dangerous at the best of times, but there's extra reason for the capital's residents to be more cautious than usual.

Posters have been spotted around Camden and Kings Cross in North London reporting a lost snake - but this is no cuddly python, or harmless corn snake - no, this is a very different beast altogether.

A missing black mamba, named Rosie, escaped from her enclosure on 5 January and people are being asked to check warm places, such as underneath car seats, under bed sheets, behind toilet seats and in washing machines - in short, all the places that you really don't want to encounter one of the world's most venomous snakes.

It is currently not known if the posters are part of an elaborate prank - the number given is not being answered and some posters have it scrubbed off.

Nonetheless, the RSPCA is investigating the claims; scientific officer for exotic animals Alexandra Jones stated: "Black mamba venom is deadly, as they are related to cobras. For this reason, mambas are considered a 'dangerous wild animal' and so require a licence to be kept. Part of the licensing process is ensuring the animal cannot escape."

Black mambas are endemic to sub-Saharan Africa and can grow up to 4m in length. They are not actually black in colour - they are so-named after the colour of their mouths - not that we'd recommend getting close enough to check. A single bite can cause a human to collapse within 45 minutes and death within 15 hours, if antivenom is not administered.

It is also one of - if not the - fastest-moving snakes in the world, and at full throttle can outrun a horse. So it's going to be tricky to catch this critter, although if it's any consolation, it will like be moving that fast away from you - like most snakes, they avoid confrontation unless threatened.

They were famously mentioned, alongside the vivid Green mamba in Roald Dahl's autobiographical book Going Solo, where he saves the life of his gardener by spotting one as it is about to attack.

Unsurprisingly, Steve Irwin didn't think twice about meeting it and giving it a cuddle.