Swapping lease for equity

A bit unusual but -

client owns a lease for which he is entitled to a rent of lets say £50k per annum for the next 10 years.

both he (as landlord) and tenant are willing to enter into the following commercial arrangement;

cancelation of the lease in return for a fresh issue of shares in the tenant company (issue of approx 5-10% of the share capital, subjected to strict shareholders agreement)

Tax implications for both?