An entry in the Guinness Book of Records lists the Whitechapel Bell Foundry as Britain's oldest manufacturing company. Established in 1570, it's been in continuous business ever since.
32/34 Whitechapel Road
London
E1
http://www.whitechapelbellfoundry.co.uk
Museum display in foyer: Monday-Friday, 9am-4.15pm. Tours of the foundry are on selected Saturdays at 10am and 2pm by appointment only. Check for details. No under-14s allowed.
Foundry tours: £8 per person