Did someone just film a giant monster in the Thames?

To be honest, we're surprised that Cloverfield was set in New York. If there's a stretch of water that's already polluted enough to accidentally produce some giant, fearsome monster, it's London's River Thames.

And it seems that it could have finally created a resident beast, going by this footage taken by YouTube user Penn Plate.

Filmed while using the Greenwich cable car, it appears to show a Loch Ness monster-style creature's 'fins' appearing out of the water, before disappearing again - but a large shadow can still be seen.

One explanation is that it could be a whale - it's just over ten years ago that the famous Thames Whale - a juvenile female Northern bottlenose whale - was discovered in the river, the first time such an animal had been seen in the Thames since records began in 1913. Sadly, she died, despite a concerted attempt, conducted over several days, to rescue her.

Could it be another whale, or something more sinister?

Frankly, the biggest mystery is why anyone was on that cable car in the first place.

Take a look at the footage and decide for yourselves.