If at any point it was your principal private residence (PPR) you can claim PPR relief and Lettings Relief.
Has it been used in a trade? - if so, Entrepreneur's Relief (ER) may be available to tax the whole gain at 10%.
The calculation will be as so:
Sales proceeds (less any costs of sale e.g. solicitor's fees) = X
Less probate value = (X)
Less any costs of capital improvement = (X)
Less PPR relief = (X)
Less lettings relief = (X)
Less annual exempt amount (2016/17) = (11,100)
Equals amount subject to Capital Gains Tax (CGT)
The basic rate band is (assuming 2016/17 and no restriction to personal allowance) £43,000. Deduct your total income for the year from this, whatever is left is the amount of capital gain that can be taxed at 18%.
The rest thereafter at 28%.
If you have a spouse and are yet to sell the property, you can transfer half of the property at a "no gains / no loss" transfer - meaning no CGT is due. However, you can then utilise two annual exempt amounts of £11,100 and potentially two basic rate bands (if available).
Make sure you have a chat with a tax adviser first!