The British Empire is coming in from the cold. For many years it was virtually a taboo subject, except when it was condemned. Now, at last, it is being revived as a subject of serious study. “Serious” does not mean “uncritical”, of course, but by any standard it was a remarkable achievement for a relatively small island state to build an empire which spanned the globe and to rule a global population much larger than its own.

Sea power was central to the process, and the National Maritime Museum has produced a video to tell the story to children. Now that even Sealink ferries are French, it is timely to be reminded that “world shipping is still largely run from London and the vast majority of everything Britain buys and sells still comes and goes by sea”.

This is a story rich in educational potential for history, geography, mathematics and economics, English, music, art . . . But this video is not the way to do it.

Its five sections, on British expansion, British trade, the movement of peoples, naval power and sea communications, are all presented by a girl standing behind a large table map of the empire. There are some excellent pictures and film footage, but there is not time to savour any of them because the wretched presenter will not stop talking.

There is no explanation of anything, and the language level is far too high for the age range it is aimed at - 11 to 15-year-olds. No one talks about “latter parts” of centuries until they are showing off at university. What a missed opportunity. Next time, Greenwich, do a lot more with a lot less.