A rare humpback whale that was seen in the River Thames just east of London over the weekend has died, according to reports. The British Divers Marine Life Rescue have confirmed it has been found lifeless in the water near Greenhithe, Kent. The charity was concerned that the whale, nicknamed "Hessy", did not have enough access to food and could be stuck in the Thames for about a week. The 5-metre marine mammal was seen several times in the Thames over the weekend and yesterday. It had travelled about 8 kilometres back and forth along the river after it was first seen near Dartford Bridge in Kent on Sunday. Humpback whales are occasionally seen off the north coast of Britain but this is the first recorded time one has ended up in the Thames since 2009. Hessy's appearance at the weekend was almost exactly a year after a beluga whale was first seen in the British capital. "Benny the Beluga" spent more than three months in the River Thames last year. Humpback whales, once prized by hunters for their blubber, can weigh up to 40 tonnes and grow to 18 metres. Humpbacks migrate tens of thousands of kilometres a year between the rich feeding grounds of the Arctic and breeding grounds in tropical waters.