CGT on sale of rental property

Other

Hello,

We are just selling one of our flats...we complete today.

We need to complete the relevant CGT forms and pay the tax within 60 days. It's all reasonably straightforward except for one point, which I hope someone here has had experience of.

Initially the flat was my husband's, bought 28 years ago. 3 years ago, when he decided to extend the lease on it to stop it falling under 80 years, he had the new lease and property title put in our joint names. Since then, the property has risen and then fallen again in price. So my 50% share would attract nil CGT once my allowance is applied, if I take a value at the point of transfer. However, I seem to remember that you can't do that....and you have to calculate the CGT as if you had owned it all along. In which case, can I also deduct half the purchase price, legal costs etc from my share? 
It' all very confusing....I tried to join the HMRC online help forum but can't get past the wretched CAPTCHA!

Thanks as always for any help.