London, Apr 12: Happy Birthday, Big Ben. One of Britain’s last bell foundries on Thursday marked the 150th anniversary of its biggest creation — the massive bell whose bongs sound the hour at the Houses of Parliament.

The 13.7 metric tonne bell was cast on April 10, 1858, at the Whitechapel Bell Foundry in east London, although it was another year before it first rang out from Parliament’s clock tower.

“We are going to toast Big Ben’s health at the end of the working day,” said Mike Backhouse, the foundry’s works manager. “Whether we’ll sing Happy Birthday, I don’t know.” Big Ben has given its name to one of London’s most famous landmarks — Parliament’s 19th-century neo-Gothic clock tower, designed by Charles Barry. The tower is popularly known as Big Ben, although the name actually refers only to the Great Bell inside. The Whitechapel foundry was marking the anniversary by casting 9cm replicas of the bell — one for every two years of its life. They will be sold for about £100 apiece.

Founded in 1570 and officially Britain’s oldest manufacturing company, Whitechapel is one of only two remaining bell foundries in the country. Its other creations include Philadelphia’s Liberty Bell and the Bell of Hope, given to New York by Londoners on the first anniversary of the September 11, 2001, attacks.

Backhouse said Big Ben remains the largest bell every made at the foundry, and would have presented a “massive challenge” to 19th-century bell-makers. “The technical challenge would have been making the mould for the bell strong enough that it wouldn’t have been broken or distorted by 13-and-half tonnes of molten bell metal,” Backhouse said. The bell cracked soon after it was installed — as an earlier version had during testing. Officials simply fitted a smaller hammer and turned the bell so the hammer wouldn’t strike the crack. The bell, crack and all, remains in use, and has become a symbol of reassuring reliability.