But is it aground?

Gold star to Tillerman for correctly getting all three parts of yesterday's quiz spot on. The prize is one pint of London Pride (or equivalent) next time Mr T is in the Putney area.

This is indeed a jack-up rig, and it's not part of some "Drill, baby, drill" project to solve the energy requirements of UK plc.

No it is indeed a much more worthy project, to stop some of the 32 million cubic metres of untreated sewage from being discharged into the Thames each year, a river used by many a rower, kayaker and sailor. Oh yuck!

The Thames Tunnel project is a proposed 32 km tunnel to the treatment plants at Beckton. It will follow the route of the river (as in the figure above) but about 75m underneath the river bed. The boreholes are part of the geological survey, with boring to start in a few years and project completion date of 2020.

So until then be careful out on the river on days after heavy rainfall.

The was also the additional question about whether it is hoisting the right signals, being the "restricted ability to manoeuvre" shapes rather than "aground".

In this case I can point those interested at the view of the relevant experts here, namely the Port of London Authority. In Notice to Mariners M9 of 2010 it clearly states that in its opinion it should use the ball / diamond / ball shapes.

I suppose their argument is that the jack / spud barge / rig thing could manoeuvre if it really, really had to, but slowly. It is touching bottom of its own accord, a bit like a kayaker holding their position by ramming the kayak into the river bed.

And Mr O'Docker is correct in that this is the tidal Thames so technically part of the British Coastline - hurrah!