This explains it in a roundabout way:

Held-over gains

Before leaving the UK, it is important to check whether an individual’s switch to becoming non-UK resident/non-UK ordinarily resident will trigger previous CGT liabilities that they have deferred by the use of holdover relief. If you  leave the UK within 6 years of receiving a gift that you elected to hold over the gains, a CGT charge could be triggered on the whole of the held over gains. 

https://trinityfinancial.ie/leaving-the-uk-capital-gains-tax-implications/