Diamond Solitaire by Peter Lovesey

Peter Diamond becomes quite the jet-setter in Diamond Solitaire (1992), the second book featuring the 48-year-old, 252-pound detective. Diamond, the creation of author Peter Lovesey, has left the police department and his home in Bath. He and his wife Stephanie are now living in London. He is working as a security guard in Harrods. Working, that is, until a young Japanese girl is found late one night curled up on a sofa in the furniture department on Diamond's watch.

Now unemployed, he decides to take on finding out about this young girl when he learns that after weeks no one has stepped forward to claim her. 

To complicate matters, the young girl, known as Naomi, is autistic and offers no clues as to where she came from or where she belongs. When she is kidnapped from the group home where she has been living, Diamond's search for her takes him from London to New York City and eventually to Tokyo. 

In the meantime he makes the acquaintance of a famous Japanese sumo wrestler, bullies and befriends the detectives in the NYC police department, has a run in with Big Pharma, and almost drowns in the East River after getting beaten up by thugs.

He is unstoppable. 

It is all great fun, really. Diamond bluffs his way into all sorts of places using his British passport and his British accent. "One useful thing Diamond had learned in the police is that anyone with an air of authority can get admitted anywhere, with the possible exception of 10 Downing Street."

The author brings in all sorts of characters to assist in the investigation and to move things along: A woman at the airport who Diamond waylays to follow a car full of suspects; a translator; a secretary with access to computer files. They are never heard from again. But, it doesn't matter. 

Although some of the twists and turns are a bit unbelievable, this is entertaining and witty detective fiction. I would advise you to suspend any disbelief and just enjoy jetting around the world with Peter Diamond. He is sparkling company.