A few weeks ago I discussed how certain American shows fail to find their audience this side of the Atlantic, with only the biggest TV geeks hunting them out. Others, meanwhile, find fans here as comfortable as they do at home. The Big Bang Theory has long been one of the most successful imports, to the extent where it has acquired a Friends­-like status. There is a genuine love for this show which other imports just haven’t achieved.

The reasons, for this are, to me, obvious. Firstly, it is well timed, in that its references to comic books, sci-fi and fantasy match a general growth in these areas. The writers wouldn’t be supplied with such a rich vein of references twenty years ago. In some senses then, it has captured a zeitgeist.

Yet it is also universal. The relationship between Leonard and Penny drove the early seasons much as Ross and Rachel were at the heart of the first few seasons of Friends. Even though their relationship is stable now, the mismatch between the two is still a rich seam. This has allowed the emotional centre of the show to move on to another couple, Sheldon and Amy, much the same way as Friends moved Monica and Chandler to the foreground over the second half of its run.

It is the expansion of the cast that has really upped the show. Some of my friends weren’t keen on Bernadette and Amy moving in to, what to them, was a boy’s show. But these voices are a minority. In fact, Amy is my favourite character, with enough social awkwardness to provide humour but enough normality not to stray into being a cartoon. The slightly awkward friendship between herself and Penny, and the even more awkward relationship with Sheldon, is both a comic delight and something with real emotional heft.

I think the fact that this show is, in essence, so simple, is exactly what makes it popular. We can identify with the friendships and relationships. Although the characters have their flaws (Howard’s a bit lecherous, Sheldon’s annoying, Bernadette’s controlling), it is pretty much just about good people trying to have a good life. Big Bang may not be edgy, but you don’t need to be when you have heart.