Chiltern parliamentary - RAIB investigation

[Railsigns]

the pioneer ATP (TPWS precursor)

ATP wasn't a precursor to TPWS; they are two different systems (as edwin_m pointed out earlier). The protection given by ATP is more comprehensive than that of TPWS. TPWS is just a quick fix until ATP (as part of ETCS) can be rolled out across the network, rendering TPWS redundant.