In 1995 the National Lottery granted money for a £4.6m sports complex, to add to Eton's existing facilities of two swimming pools, 30 cricket squares, 24 football, rugby and hockey pitches and a gym. The College paid £200,000 and contributed 4.5 hectares of land in return for exclusive use of the facilities during the daytime only. The UK Sports Council defended the deal on the grounds that the whole community would benefit, while the bursar claimed that Windsor, Slough and Eton Athletic Club was "deprived" because local people (who were not pupils at the College) did not have a world-class running track and facilities to train with. Steve Osborn, director of the Safe Neighbourhoods Unit, described the decision as "staggering" given the background of a substantial reduction in youth services by councils across the country, a matter over which, however, neither the College nor the UK Sports Council, had any control. The facility, which became the Thames Valley Athletics Centre, opened in April 1999.
Try to answer this question if possible (otherwise reply "unanswerable"): When did the Thames Valley Athletics Centre open?
April 1999