Sherlock faces his biggest challenge of all – delivering a Best Man’s speech on John’s wedding day! But all isn’t quite as it seems. Mortal danger stalks the reception – and someone might not make it to the happy couple’s first dance. Sherlock must thank the bridesmaids, solve the case and stop a killer!

Written by Stephen Thompson, Mark Gatiss and Steven Moffat, the episode airs at 8.30pm on Sunday 5 January on BBC One. To whet your appetite, here are ten teasing lines of dialogue from the episode…

» ‘Is that a brain?’

» ‘The famous Mr Holmes! I’m very pleased to meet you, but no sex, okay?’

» ‘Do you know any funny stories about John?’

» ‘Two people who are living together are about to attend church, have a party, and then go on a short holiday; what’s so big about that?’

» ‘Oh, by the way, Sherlock – do you remember… Redbeard?’

» ‘Back up! I need maximum back up! Baker Street! Now!’

» ‘Sorry, there was a lot more deduction there than I was expecting.’

» ‘I think I had dinner with a ghost, Mr Holmes.’

» ‘Vatican Cameos!’

» ‘It’s the end of an era, isn’t it?’

> Find out all the details on Series 3 so far in our summary.

Are you looking forward to ‘The Sign Of Three’? Let us know below…

> Order Series 3 on DVD on Amazon.

> Buy the Series 1-2 boxset on Amazon.

Watch the Series 3 teaser trailer…