Jamesgr George

My wife and I bought a flat for £13000 16 years ago.my granny lived in it for 2 years then she had to go into a retirement home.we let the flat out for 14 years.we are living in a bungalow which is too big for us and we hope to move into the flat.If we move into the flat for 10 years and then sold it how much capital gains tax would we have to pay.The flat is now worth £85000