CGT Base Cost where there was a Life Interest

I shall be grateful for insight on the following situation:

Our client's mother died in Mar '02 leaving property to our client subject to life interest of grandmother, who lived in the property. Value was £100,000 taking into account the life interest.

Grandmother died Jan 04, and at this date the value was £150,000 with vacant possession.

If our client now disposes of the property, what is the base cost for CGT purposes? Is it the Mar 02 value or the Jan 04 value?

Robin Dillamore