Fort Halstead, now used by DSTL. During World War I, part of the London Defence Positions scheme was resurrected to form a stop line of trenches, in case of a German invasion. North of the Thames, the line was continued to the River Lea at Broxbourne rather than stopping at Epping. South of the Thames, it was continued to Halling, via Wrotham, linking to the Chatham defences. At the western end the line was stopped short at Buckland Hill, just beyond Reigate Fort. At Guildford, houses have been built on the Pewley Hill site, but Henley Fort (aka Henley Grove) has been well preserved as a youth education centre. It could be seen on a Heritage Open Day. Reigate Fort Reigate Fort has been owned by the National Trust since 1932. The structure was falling into disrepair, but grant money from the Biffaward, the Heritage Lottery grant and the National Trust itself has enabled the Trust to restore the building. The first phase of the repairs was carried out in 2000 and was funded by a grant of £104,000 from the Biffaward. A second phase cost £174,000. The fort opened to the public free of charge in 2007, though restoration work is ongoing. Information boards have been installed to tell visitors about the buildings. A teacher's pack is available and educational visits can be arranged. See also Fortifications of London Outer London Defence Ring - the idea revived in World War II References External links London Mobilisation Centres - Gazeteer (includes map) National Trust - Reigate Fort Handbook for the London Defence Positions Fortifications of London Defence of London