The fact that Dover, Harwich and Southampton are ‘London’ – in the eyes of American cruise lines at least – is a constant source of amusement. The idea that ports about 80 miles away can be considered part of the capital stretches even the Ryanair concept of geography beyond breaking point.

But given what London itself can offer to passengers embarking or arriving by cruise ship, perhaps it’s not a bad thing after all.

There are plans to build a cruise terminal at Greenwich. If they are ambitious enough, it can’t come soon enough, for the historic waterway that is the River Thames is less than welcoming at the moment.

There are three main cruise berths, each with its own history. First to be reached, passing up-river, is Tilbury, used regularly by Cruise & Maritime Voyages and occasionally others including Fred. Olsen. Its 1930s-built terminal welcomed Britain’s first large group of West Indian immigrants, who arrived in 1948 on the Empire Windrush, but its facilities are long overdue an update.

Greenwich has even more history; the Old Royal Naval College is a UNESCO World Heritage Site. Designed by Christopher Wren, it was built in the 17th century on the site of a royal palace. Today’s cruise ships have to moor in mid-river and passengers are taken ashore by tender. It’s a process that can be achingly slow, as guests arriving on Viking Star in May discovered. At 228m, Viking Star was the largest cruise ship ever to use the Greenwich mooring, to be fair, but some passengers were held up for so long trying to disembark that they were in danger of missing their flights home.

Tower Bridge is an even more spectacular setting for a berth, but just because it’s closer to the centre of the city doesn’t mean it’s any easier to get ashore.

Ships tie up alongside HMS Belfast, but passengers are taken across the river by boat to Tower Pier on the north bank. This means hanging around waiting for tenders. Why can’t they be allowed to step ashore on the south bank?

The River Thames is less than welcoming at the moment for disembarking passengers

Outline planning permission has been granted for Greenwich’s new terminal, but progress towards its construction is proceeding at a pace that makes the evolution of Heathrow’s third runway look supersonic.

Time for London mayor Boris Johnson to give it a kick-start – if he’s not too busy with his duties as MP for Uxbridge and South Ruislip or with his ambitions to take over from Prime Minister David Cameron.