Well , they tried to get a rope out onto my fathers pontoon , he was standing there and as ex Lifeboat Operations Manager for Teddington , he phoned London Coastguard direct and requested immediate launch , as such they did so without going through the current launch authority , which saved time.
They weren't attempting a planned mooring , the pontoon in question is locked and is private , they would have had no reason to moor on it.
It was a couple on board , man and woman and two cats. The stream was flowing very quickly and it happened literally in seconds. To be honest it was madness to be attempting to head up our weirstream in that boat in those conditions. Teddington Weir is the biggest and most powerful weir on the Thames.
Exactly what you said happened , happened. The cockpit of Tantalus is at the back of the boat , everything happened so quickly , the only opportunity was to chuck a stern line out from right where they were standing. A better idea would have been the anchor. If the rope had missed the pontoon , and they hadn't got an anchor out , the boat would have been broadside against the downstream moorings and probably broken in two , damaging all the moored boats there.
The boat on the pontoon in the big photo is Brown Owl , another Dunkirker.