Whenever reading to my two-year old son, it pleases me to imitate the various accents of the characters in the books he loves so much. Thomas, Bob, Pat and the cast of Balamory all feature with reasonable authenticity. However, Fireman Sam and the Welsh accent completely elude me. I sound like... well, we all know the typical result of a bad Welsh accent.

Why is the Welsh accent so difficult to imitate and are there any tips and tricks to improving it?