Zoe died on 17 February 2015. She had made the following gifts during her lifetime:

(1) On 7 March 2010, Zoe made a cash gift of £270,000 to her son as a wedding gift when he got married.
(2) On 21 June 2010, Zoe made a cash gift of £620,000 to a trust. Zoe paid the inheritance tax arising from this gift.

Zoe’s husband had died on 25 July 2007, and 20% of his inheritance tax nil rate band of £300,000 for the tax year 2007–08 was not used.

The nil rate band for the tax year 2009–10 is £312,000, and for the tax year 2010–11 it is £325,000.

Required:
What amount of marriage exemption will be allowable here?