This is a warning to Sarah Treseder, incoming chief executive of the RYA. Her accredited sailing schools may soon be receiving applications from Saudi nationals wishing to learn how to hoist sail, but not how to moor up.

For a new terror target could soon be on the cards for anti-western jihadists. This one’s a belter: much easier than the sky-scrapers which required the technical mastery of having to learn how to take off, but not to land. It’s an airport slap bang in the Thames Estuary. All you have to do is sail in and detonate: no-one can monitor every ship coming through the world’s busiest seaway – the Dover Strait – which is adjacent to the proposed airport and by the time the footings are in place even the Somali pirates will have learned how to mask their gunboats as windfarm tenders.

It has been reported that the new airport is to be sited two miles off Sheerness – this is very close to the wreck of the SS Richard Montgomery (pictured) which is loaded with enough unexploded ordnance from World War II to set up a 2m tidal wave should it go off.

The estuary is also home to one of the biggest areas in Europe of migrating water-fowl who are not jet engine savvy. And it is the gateway to the Thames Barrier, which is creaking at the joints as sea levels rise. Further constriction of the fierce tides which ebb and flood twice daily may put them under terminal pressure and therefore London’s Underground at risk of flooding.

But doubtless Messrs Johnson and Malthouse will have explained this already to the sheikhs hoping to cash in on this property developing opportunity.