Hi CG31
It's not a change of circumstances, but it may bring into force Tariff Income.
www.entitledto.co.uk/help/savings-assumed-income It would depend on your friends age, how long he would go over £6k.Your friend if under state pension age should inform relevant authorities of any increase he has in savings that take him above the threshold, his means tested benefits would be affected by Tariff income.
Gary