There is a stoplight. He gets a kiss on the cheek while they are stationary, and then on they go.

At the door, the gatekeepers insist that Bella and Sherlock prove that they are together - "you can't just pretend to be dates to get in, you have to actually be!" - and another kiss occurs by way of proof, and in they go.

The Viennese Carnival thing is halfhearted - a few people have made attempts with the outfits, but almost no one has bothered with a mask, and most are neglecting the theme entirely. Still, all the couples present seem happy to be there.

"If you spot anyone who snuck past the gatekeepers without a date," she says to Sherlock, "point 'em out."