1938. Few Mark 2 multiple units were built but some driving trailers were introduced for Gatwick Airport express services, then operated by the InterCity brand. British Rail built a fleet of electric units to operate Bournemouth services from Waterloo in the 1980s, with Mark 3 bodies and plug doors. These Class 442 (5-WES) units later transferred to the Brighton Main Line in 2008 on Gatwick Express services from Victoria, ran by the Southern franchise, before returning to South Western Railway in 2019. The last slam door units ran in mainline operations in November 2005. New safety regulations prohibiting the use of trains with slam doors (unless equipped with secondary or central locking) were not introduced until the last examples could be withdrawn. Exceptionally, some slam door units were allowed to stay in service for another couple of years by special derogation on the Lymington Pier "heritage" branch before they retired permanently in 2010. Some Mark 1 units have been preserved by heritage railways ever since. Major accidents A lack of investment and focus on infrastructure maintenance and collision safeguards across institutions led to a marginal improvement in the net rate of fatal incidents compared to the same (non-British Rail) period before nationalisation, which reduced potential passengers' confidence. The British railway industry failed to keep track with the safety regime of its aviation industry, which by the 2000s became its national precedent and contributed to a swift decline in fatalities. 2 December 1955: 11 passengers died and 41 were injured when an electric passenger train from Waterloo to Windsor and Chertsey (dividing at Staines) collided with the rear of a goods train. The accident occurred in thick fog and was caused by irregular block instrument operation by the signalman at Barnes Junction. 4 December 1957: 90 passengers died and 173 were injured in a collision in thick fog near Lewisham in south London, which also caused the collapse of an overhead rail bridge on to the wreckage below. The number of deaths was the third highest ever in a British railway accident. 5 November 1967: 49 people died and 78 were injured when a train from Hastings to Charing Cross was derailed by a track defect outside Hither Green station. Amongst the survivors was Robin Gibb of the Bee Gees. 12 December 1988: 35 people died and 100 were injured when three trains collided near Clapham Junction because a signal circuit