Already the most expensive in Europe – Britain’s rail fares just keep going up and up.

So why are the railways so expensive? Panorama investigates how your money is spent on the railway and lifts the lid on a world of overspending and secrecy.

While researching the programme, producer Toby Sculthorp discovered how difficult it was to actually find out how our money was spent on the railways.

“The starting point for the programme was the fare rises in January. I then found out that the majority of that is spent on Network Rail improving and upgrading the network," said Toby.

"Unfortunately there is a long history of overspending – by as much as a third," he added.

"I really began to take notice when I came across some very interesting work carried out by William Perrin at kingscrossenvironment.com.

"William – a former civil servant in the Cabinet Office – knows his way around Whitehall and even he found it nigh on impossible to get a straight answer on how much Network was over spending on Kings Cross.”