Andy

I bought a house for primary private residence in 2000 on a residential mortgage. I lived in it until 2005 and transferred to a BTL mortgage and releasing £10,000 equity from the property. In that 5 yrs to 2005 the property increased in value by £10,000. I have let the property out since 2005 and the property value has only increased a further £5,000. Would I be subject to paying CGT on the full £15,000 gain in value since I've owned the property from 2000? Or just subject to paying CGT on the £5,000 gain in value since I've had a BTL mortgage from 2005? Thanks