As it happens, Hull is on a rather important trans-European route that apparently runs from Moscow to Limerick. Millions of people each year disgorge from giant North Sea ferries in Hull and race through, ignoring the city completely. The strategy is to capture some of these transients, who will all see the mysterious form of The Deep as they approach their docks. There will be cheap all-in excursion breaks from London. Schools are massively pre-sold, so no problem there. And a vital new pedestrian footbridge will link The Deep across the River Hull to the city’s old town.

But just to be on the safe side, Brown has financed The Deep in such a way that it will start life with zero debt, and needing only 190,000 visitors a year to break even. He refuses to forecast beyond that very conservative figure, although he mentions that independent consultants Coopers and Lybrand have suggested visitor numbers ranging from a “pessimistic” 250,000 to an “optimistic” 500,000. He deliberately chooses to be considerably more cautious than his advisers: a Yorkshire characteristic, he cheerfully admits.

One thing the millennial building bonanza has taught us all is that when it comes to predicting visitor numbers, you might as well pick the number on your Lottery ticket. For every Eden Project, there’s an Earth Centre. We know that art galleries and museums pull in big numbers, we know that some science-based centres such as Magna in Rotherham do very well, but as to whether a "Submarium" in Hull can do the business: well, you’ll tell me soon enough because, come Easter, you’ll either go there or you won’t.

All I can tell you is that this is the best Terry Farrell building I’ve seen in years. His tough, allusive architecture is just right for this industrial-marine setting. Farrell was never one for the dainty detail, always preferring the felt-tip pen and the colour marker to the 9H pencil. And although he is no slouch when it comes to deploying advanced technology, he has long since moved away both from the refined high-tech aesthetic and the post-modern experiments that followed. His client knows exactly what he’s up to. “If this building was a man,” Brown observes, “it would be wearing a tattoo”.