London trip, which Lens(es) to take ?

I'm facing a similar challenge with a trip to Greece and Turkey for my wife's birthday. I've bitten the bullet and decided the trip is more about her and our relationship than about my taking advantage of all the photo opportunities. So I'm taking my D5000 and 16-85, with a few accessories. You only have four days--I'd focus on seeing the city together, not the photos. You really can't do both--and you don't want your wife feeling like second fiddle to the Nikon.