LONDON • Visiting Washington during the height of the North American summer is always an unusual experience.

The weather is unbearably hot and clammy. But the United States capital city is also serene and largely deserted. Congress is in recess, the politicians are out of town, senior civil servants take their annual holidays, and the city's top restaurants struggle to eke a living out of stray tourists, rather than the diplomats or lobbyists on fat expense accounts who provide their traditional sources of revenue.