It's four metres long, the weight of two grizzly bears and dangerously delicious. The Bluefin Tuna is back in British waters so Tom Heap and Helen Czerski are here to celebrate the role of the tuna in food, culture and nature. Unseen since the 1960s, these enormous fish have surprised surfers and anglers by leaping clear out of the waters of South-West England. Rare Earth takes a deep dive with the tuna to examine their unusual biology and their cultural importance to people all around the world. They can live up to 60 years, dive up to 1km below the ocean surface and swim as fast as 40 km per hour. Unfortunately for the bluefin, they’re particularly tasty, prized for their meaty sashimi, with some fish reaching prices close to £2m in the ceremonial new year auction at Tokyo’s fish market. Tom explores the intense Japanese relationship with tuna while Helen makes a plea to give this fish the respect it deserves- we should celebrate its extraordinary biology rather than stuffing it in a tiny can with a ‘dolphin-friendly’ stamp on the label. Producer: Alasdair Cross Assistant Producer: Toby Field Rare Earth is a BBC Audio Wales and West production in conjunction with the Open University