Most notable of all, however, it made an overnight star of its Holmes, Benedict Cumberbatch. Previously the kind of well-respected theatre actor who popped up in award-winning thinky dramas on BBC Two, Cumberbatch – with his clay-white skin, sexy-sloth face and pub-time jaguar growl – became instant pin-up totty; eventually going on to become GQ magazine’s “Man of the Year”, and be hailed by Steven Spielberg – who then cast him in his forthcoming War Horse – as “the greatest onscreen Holmes”. Sherlock has changed Cumberbatch’s life.

Entering the room today, the discrepancy between Cumberbatch and Cumberbatch-as-Sherlock is notable. Holmes would enter the room in a swirl of greatcoat, rattle off some nail-gun comment, analyse the contents of the biscuit tin to deduce that it’s someone’s birthday, then go into a high-grade petulant intellectual sulk.

Cumberbatch himself, on the other hand, is wearing a faded band T-shirt, and exudes the air of an indie kid in his late teens or early twenties. He’s bright and enthusiastic and friendly – his is the air of someone who helps mums carry buggies up stairs.

When the read-through starts, however, this gonky teenager disappears, and he slips, effortlessly, into the stiff-backed, cold-eyed, Pentium 20 brain of Holmes. His delivery can still the room – even in his T-shirt, in this bright summer sunshine. Spielberg was not wrong.