According to Subbrit the bunker, which is located beside a small reservoir is officially listed by Thames Water as a personnel shelter and is about 3 miles from their Latton Control Centre. It was built in the 1980's after Thames Water moved their headquarters out of London.
Built to protect the inhabitants against blast and radiation for 12 people up to 30 days, the bunker has its own water supply, generator and would be totally self-sufficent. There are several thick concrete blast doors and the bunker is in excellent condition. The lights still work, the decontamination shower is still in situ as are the generator, air filters, water tank, toilets and basic kitchen facilities.