Guest house glitch

Our client ran a small hotel/guest house as a sole trader for just over three years and on sale made a net capital gain of £135 000. With full business asset taper relief the tax is around £10 000. However if we claim main residence tax relief on the 3/11ths that was occupied by our client and his family the capital gain on the balance is calculated as a mixed-use asset with taper relief at only 5% on 3/11ths of the gain after main residence relief. This increases the tax to £20 000. We should like to claim business asset taper relief on the whole of the hotel without main residence relief on the grounds that it was necessary to the business that the proprietor and his family live on the premises and thus the whole of the property was a business asset despite...