Michael Gilbert 
End Game [PDF ebook] 

The London Regional Crime Squad, is trying to nail a financial empire involved with organised crime and drug smuggling. David Morgan goes undercover and is hired by a travel company to act as a tour guide around Europe, but is in fact being used as a drug mule. Eventually, he also finds himself posing as a homeless vagrant in order to track down a former employee of the financial empire who knows of the whereabouts of incriminating documents. This is a ’Snakes and Ladders’ operation with twists and which ranges from London to Florence.