Juvenile minke whale has been put down after its condition deteriorated London: A juvenile minke whale that became stranded in London's River Thames has been put down after its condition deteriorated and vets decided it could not survive in the open water. The whale, measuring three to four metres (10-13 feet), was first spotted in southwest London on Sunday and was washed ashore at a set of gates controlling water flow. Rescue efforts by the British Divers Marine Life Rescue (BDMLR) service and firefighters failed when the whale slipped its leash and then swam upriver, instead of towards the sea.