London - Sports enthusiast reckon it's set to become the most popular subterranean whitewater freestyle kayaking/waterboarding site in all of Europe amid confirmation it dwarfs its surface counterpart from Boulters Lock at Maidenhead to Devil's Island near Henley.
Located some 4km under the Thames the new flow was discovered using data amassed from 241 abandoned deep wells left over from drilling by energy industry midget Wannabe Oil.
Environment Agency sources said today they'd wanted to call it the Abu Hamza Mk II after an underground Amazonian tributary in Brazil.
But a member of the public pointed out it goes against the grain to use the UK terrorist's name for silly sentimental reasons - even if parts of the waterway resemble the daft-as-a-soused-herring's metal hook arm.
The watercourse's discovery means Thames Water's plans for a storm drain under the Thames have ground to a halt as environmental protests against pumping a lot of polluting shit gathered apace.
"Besides, there'll be hell to pay for if all that crap ends up polluting the Amazon water table in Brazil," a green activist wrote on the water company's website today, "given that Mayan calendar prophecies reckon that's where its source originates."
More test drilling is expected later next month once all danger of equinoctial high tides has passed.