The Welsh tongue twister "Rowliodd Lowri lawr yr allt" is difficult to say at best, but it's even harder for those who cannot pronounce the 'r' correctly.
In the S4C programme Rowliodd Lowri on Tuesday, 19 June, we will look at the phenomenon of the 'r', which is very common in Wales, by listening to the experiences of different individuals. Producer Dafydd Parri explains.
"The 'r' speech impairment is an interesting phenomenon. I myself have difficulty saying the 'r', and I'm very aware of it when I speak. I wanted to explore the subject in a light- hearted way but without making fun at people either," explains Dafydd, adding that he, his brother, mother and one of his own daughters share the same trouble.
The guinea pig in the programme is the entertainer and famous 'r'er Dilwyn Morgan. We follow him as he receives speech therapy to try to change the habit.
"I'm not sure when I first started to 'r'," says Dilwyn who lives in Bala. "I have no memory of it as a child. But as I got older and went to Secondary School the other children would make fun of me, and it took me a while to realise why.
"As I got older too, after leaving school, it was something I was very aware of. Even today when I write a script or read something I sometimes change a few words to avoid having a lot o 'r's together. "
Dilwyn goes to see Language Therapist, Marian Trithal, at Alltwen Hospital, near Tremadog. Session by session, we will follow his treatment. Will he succeed, and what will his response be?
In the programme we will also talk with some of Wales' other famous 'r'ers including comedian Ifan Tregaron and we will find out about the different types of 'r'ing which belong to specific regions of Wales.
Also, what causes it? Is it laziness? Or is it something genetic or something that is common to a particular area?