This looks great if the clip is anything to go by.
I think it's just a one-off for Christmas and to celebrate Ronnie Corbett's 80th birthday; made by a lot of today's comics and writers to pay homage to the little fella and of course his erstwhile partner Ronnie Barker. It's being broadcast on Christmas Day on BBC One at 5:10pm and looks to be one worth staying awake for.
I'll be really surprised if there are any characters repeated or runners within the entire 50 minutes (might of course get shot down in flames with that prediction - but I have faith).
https://www.comedy.co.uk/tv/the_one_ronnie/videos/2097/blackberry_sketch/