Velvet, the gift will be regarded as a PET (potentially exempt transfer).
This from the HMRC website (The taxt in bold font is the most relevant)
Any gifts your mother make to individuals will be exempt from Inheritance Tax as long as she lives for seven years after making the gift. These sorts of gifts are known as 'Potentially Exempt Transfers' (PETs).
However if she gives an asset away at any time, but keep an interest in it - for example she gives her house away but continue to live in it rent-free - this gift will not be a potentially exempt transfer.
If she dies within seven years and the total value of gifts she made is less than the Inheritance Tax threshold, then the value of the gifts is added to her estate and any tax due is paid out of the estate.
However, if she dies within seven years of making a gift and the gift is valued at more than the Inheritance Tax threshold, Inheritance Tax will need to be paid on its value, either by the person receiving the gift or by the representatives of the estate.
If she dies between three and seven years after making a gift, and the total value of gifts that she made is over the threshold, any Inheritance Tax due on the gift is reduced on a sliding scale. This is known as 'Taper Relief'.