The limit for bringing undeclared cash across an EU border is €10,000 (12,200 francs), but customs officers told German financial magazine Wirtschaftswoche that drivers regularly broke this limit in 2013.

They found €573 million in illegal money, while in 2012 they found just €9.3 million.

But smugglers were also finding more cunning ways to avoid being caught. “More often we are finding cars with four or five people inside and each has around €9,800 or €9,900 in cash on them,” Hagen Kohlmann from the Ulm customs authority told the magazine.

When this happens, it is hard to prove who the money belongs to – so no one can be punished.

Other items turning up more often included keys to bank vaults, a sign, Kohlmann said, that people were going over the border to empty their accounts following last year's crackdown on overseas tax evasion.

Luck also seems to be running out for those who try to dodge the notoriously tough officers along the German-Swiss border by going through Austria.

Austrian border control found more than a million in smuggled money in 2013 – more than twice the amount from the year before.