Neat. This is an “official” photograph from the UK Prime MInister's Office. I've actually walked up those stairs when I was covering Harper's first visit to 10 Downing Street in 2006 (A Mr. T. Blair was the occupant at that time).
I believe the the photos you see lining the stairway are portraits of the various prime ministers that have occupied the house at 10 Downing since George II gave the place to Robert Walpole in 1732.