A business activity?

My mother-in-law died in January 2004. She was an author and left her 98% shareholding in her company to her two children being my husband and his sister — who already held 1% each. The company was valued by the accountant and agreed by HMRC at £1 000 000. HMRC agreed that copyrights were relevant business property and that inheritance tax business property relief was due on the company shares. However the main value of the company is in a share portfolio valued at approx £800 000 and the point at issue is whether the shares are excepted assets or not.
HMRC are arguing that the share portfolio is part of a hybrid business alongside...