Whitehall was left combing its season ticket loan records this weekend as another set of top secret papers did the rounds of the 5.45pm from Waterloo.

Just days after a Cabinet Office worker left a stack of top secret anti-terrorist papers – including an analysis of Al Qaeda - on a train to Surrey, it emerged that a second set of papers detailing Treasury Dept efforts to fight financial fraud had gone walkies on another train around the same time.

As well as detailing weaknesses in how the HMRC’s computer systems can counter fraud, the papers covered government efforts to counter terrorist financing and money-laundering, and ways in which the finance system can be manipulated to finance Iran’s development of weapons of mass destruction.

Apparently the papers were left on a Surrey-bound train last Wednesday, the same day that the Cabinet Office papers were mislaid on another Surrey-bound train. The Cabinet Office papers were immediately passed on to the BBC which handed them back to the government – albeit on camera. The finance papers found their way to the Independent on Sunday, but not apparently until Sunday.

The question of what happened to them in the meantime will cause someone in Whitehall absolute nightmares. Still, if nothing else, the fact that they were passed on by an Independent on Sunday reader will dramatically narrow the hunt for the picker-upper.

The Surrey-bound civil servants’ apparent carelessness with top secret papers is just the latest in a tide of government data breaches. If civil servants aren’t losing CDs with the details of every family in the UK, they’re leaving laptops chock full of details of servicemen in the pub.

Out of their brains on the 5.15

Whitehall has already launched an investigation into the loss of the Al Qaeda documents, and the civil servant responsible has been suspended.

Home secretary Jacqui Smith has been summoned by MPs to explain how the gaffes might affect the fight against terrorism. Her department didn’t actually lose any of last week’s papers. In fact, Smith is unlikely to ever leave secret papers on a train, given that she rarely walks the streets of London, never mind takes public transport.

According to The Times, a Treasury spokesman said of the latest gaffe, “We are extremely concerned about what has happened and will be taking steps to ensure it doesn’t happen in the future.”

Sadly, with this government’s record the surest way of clamping down on civil servants leaving important documents on trains is to let the operating companies jack up train fares so that even Whitehall fat cats have to get on their bikes. ®