Martha Kearney visits the Menai Strait - the stretch of water which separates Ynys Môn or Anglesey from mainland Wales. She learns about its treacherous tides and hears about the history of its two bridges, both built in the 19th century to improve travel between London and Ireland. The Menai Suspension Bridge was designed by Thomas Telford and will celebrate its 200th anniversary at the start of 2026. The newer Britannia Bridge had to be completely rebuilt after a disastrous fire in 1970.

Martha meets an academic from Bangor University who explains how ocean physics make the waters of the Strait so dangerous. At low tide she braves the pouring rain to go rock-pooling with a wildlife expert, who explains why the Strait is such a special habitat for marine life. She also visits Church Island - a tiny island in the middle of the Strait which is home to an ancient church - and meets the people who look after it.

Producer: Emma Campbell