Help me remember the book

[casawasa]

I thought it was Robert Harris but can't find it. Young man ends up in a mix-up with important papers from a drug company. He ends up living "off grid" in london. Hired killers chase him but he leaves his old life and lives rough on the margins of society.
Which book? Help?
Thanks

I feel like I know it, but can't quite remember. I'm thinking of a film though. I seem to remember a bag switch.

The one with Will Smith?

Enemy of the state?

Thanks but it's a book set in London. It was a great read.
Thanks for the replies

Could it have been a book which was made into a film OP?

Ordinary Thunderstorms, William Boyd??? Pretty sure that's the one.

Greatresult is right.

If you enjoyed Ordinary Thunderstorms, then Restless and Waiting for Sunrise by the same author are also worth a read :)