In May, what was billed as the biggest ever overhaul of train timetables led to widespread rail disruption - why has this new timetable caused such rail chaos this summer?

Since then, passengers travelling on the services of two rail franchises - Govia Thameslink and Northern - have suffered weeks of cancellations and delays.

Transport Secretary Chris Grayling has defended his handling of the situation and pointed the finger at the rail industry - but who is really responsible? And can long-suffering passengers trust that the disruption will finally be brought to an end - and not repeated?

David Aaronovitch assesses what led to such chaos on the railway and what the disruption says about the state of Britain's railways.

CONTRIBUTORS

Tony Miles, Modern Railways magazine

Dieter Helm CBE, Professor of Economic Policy at Oxford University.

Lord Adonis, former Transport Secretary and former Chairman of the National Infrastructure Commission.