The oldest building in the area?

What is the oldest building in Hampstead and Kilburn?

A daft question you might think but with no remaining habitable fragment of Kilburn Priory and no surviving medieval church I think this is a harder question that might be thought...

My instinct and guess is that it is Fenton House in Hampstead.
http://www.nationaltrust.org.uk/main/w-vh/w-visits/w-findaplace/w-fentonhouse/

It is dated to 1693 - Willam and Mary are on the throne of England, the dodo becomes extinct in this year, France is at war with the Palatine (Germany) and John Harrison, a famous clockmaker buried in Hampstead parish churchyard is born.

The house was owned by Joshua Gee who was a silk merchant (i.e. wealthy) and this was a classic mansion house of it's period. The name of the house however comes from Philip Fenton another merchant who bought the house in 1793. This family made a number of the changes and features that survive today in particular the walled garden.

Some pictures of the house and gardens can be found here http://www.flickr.com/search/?w=all&q=Fenton+House&m=text

But more to the point, is there anything older in Hampstead and Kilburn?