The Circus Train Conspiracy #14 (Railway Detective) by Edward Marston

Following a string of successful performances, the Moscardi Circus is travelling by train to Newcastle for their next show. Yet a collision on the track with a couple of sleepers causes pandemonium: passengers are thrown about, animals escape into the night and the future of the circus looks uncertain.
When the body of a woman is discovered in woodland next to the derailment, Inspector Colbeck is despatched to lend assistance, believing the two incidents might be connected. It is up to Colbeck to put the pieces together to discover the identity of the nameless woman and unmask who is targeting Moscardi's Magnificent Circus.