Having formed in Derry in 1976, it’s a fact universally acknowledged that The Undertones have spent the last 40 years establishing and re-establishing themselves as one of the country’s most treasured acts. With their equally enduring legacy, back catalogue and inimitable charm, the band have just marked the milestone by recording a special live show for BBC Radio Ulster in front of a live studio audience at Blackstaff in Belfast. Hosted by Stephen McCauley, the resulting one-hour programme – set to broadcast on BBC Radio Ulster and Foyle at 3pm on Monday afternoon – is a perfect distillation of why the band are still a homegrown live proposition at the peak of…