Work Advent Calendar 2017 Day 18: Two Ronnies trailer, 1978

They may have had Christmas Night with the Stars 1971 and 1972 as their personal fiefdoms but even with the superior BBC double act having defected Yarwood, Spencer and, um, True Grit: A Further Adventure held sway on the 25th in this year, Barker and Corbett having to wait until 1981 for the most prime slot of all. In the meantime their Boxing Day show doubled as the start of a new series. Is that why they appear to have jokes left over for the trailer? Or why the audience are so easily pleased?