You’d have to go back more… to after the
first season of Sherlock aired. Maybe even further than that because
they would have met in 2007/2008 to film the Unaired pilot was submitted
to the BBC in 2009. ASIP filmed in 2009.
Mofftiss announced the Sherlock pilot at the Edinburgh International
Television Festival in August 2008, and that it would be televised in
mid- to late- 2009. We have to assume that casting and filming had
already been done or that announcement would have been verrrry premature, so Martin and Ben had met sometime before August 2008.
Then you’ve got to add the amount of time needed for filming (current episodes take 4-5 weeks each, but we can adjust that down a bit), then add in the time it takes to do casting, which we know was more than a month, because Martin waited at least that long in between his initial audition and when he came back to do his final one with Ben, so I’d say it was no later than June 2008; and that would be with the entire project going apace like a rabbit on speed, so they probably met even earlier than that.
The earliest pics I can find of them together are from September 13, 2009 at the premiere of Creation, in which Ben had played the part of Joseph Dalton Hooker.
They seem very couple-y at this point in time:
And of course, this is also the thigh-grab event:
Anyone have anything with the two of them before this?