Their sounds have marked history's turning points: American victory in the Civil War, the death of monarchs, the collapse of governments. These are the bells of the Whitechapel Bell Foundry, still standing proud in the heart of London's East End, and with a list of head craftsmen going back over five centuries. Big Ben was their greatest ever challenge, so large that the Tower of Westminster had to be built around this giant of instruments. Built to the clockmaker's specification, and contrary to Whitechapel's blueprint, the bell cracked almost immediately (the resulting bodged repair with the Victorian equivalent of Polyfilla gives it the characteristic 'bong' we have come to love.) But many of Whitechapel's stories are much more earthbound. Harold Rogers must be one of the UK's oldest bell ringers. Aged 90, he still rings regularly at the church in south-west London where he met his bell-ringing wife. And thanks to the skills of the Whitechapel workforce he's about to become reacquainted with some very old friends. At the outbreak of WW2 Harold was one of the regular ringers at the church of St-Magnus-the-Martyr, whose bells were taken down for safety in the war and subsequently sold for scrap. 60 years later, replacements are finally being cast by Whitechapel, and Harold is perhaps the only man who will know for sure whether the new bells sound as good as the old. As the new bells are cast we meet the colourful characters behind this typically proud East-end institution. There's Nigel who masterminds the moulding, always ready to leap to safety should disaster strike during the pouring of molten metal. Steve and his young apprentice prefer the relative tranquillity of the handbell workshop, full of the delicate sounds of miniature bells being tuned to perfection. And leading them all is Alan, the Master Founder, who inherited the business from his father and his grandfather before him. Through him we hear about the foundry's unique work during the war, turning its skills to the production of submarine detection equipment for the Admiralty. And from the foundry's safe Alan pulls some remarkable documents charting the foundry's history, including the inside story on what really went wrong with Big Ben. As for Harold, he doesn't just get the chance to hear the bells of St Magnus ring once again, but grabs the opportunity to join the ringing team. And at the end of the rope is a special bell, dedicated to his late wife who rang with him in the same tower 60 years earlier. It's a moving moment, a piece of Whitechapel magic, a reminder of the power of bells to bring us all a little closer together.