I did too. Les Dawson absolute class. Many years ago he was appearing the Stardust Club, near Usk. I was working in Monmouth and word went round that Les and his wife were in the Punchbowl Inn and as long as he had a drink in front of him he would carry on telling jokes. I didn't get back to work that afternoon.
Saw an interview with Les many years ago when he was asked about the silent "mouthing" of words in his sketches with Barraclough - the sketch in the OP was typical. He said it was very common in Lancashire, and had come down through the generations of cotton mill workers into normal society. It was a lip reading method used by the workers inside the mills to communicate. It was so noisy in there normal speech was impossible - the clatter of the looms meant you couldn't hear a thing.
Blankety Blank with Les at the helm was worth watching; unlike this modern horlicks of an effort Ps Roy Barraclough as well - Corries been a pale shadow without Alec Gilroy