tennant in sja s3?

as we all know david is still filming dr who at the moment and sja has started filmingbut they're being very secretive. Apparently Tennant was at the read through for SJA which obviously indicates he's going to be in one of the episodes, but thats about as far as we know.
Until now!
On the 20th April there was some filming in Penarth which included Tennant and the TARDIS. It might have included other things but the security was very very tight.
and david is wearingthe same clothes as he is for the last special, which can only suggest that this is him in an episode of SJA!