Four-way split

I would appreciate readers' help with the correct capital gains tax calculation for the following new client — one of four brothers for whom the similar calculations will apply.

A holiday property was purchased by the brothers' parents in November 1986 for £75 000 purely for weekend and summer breaks for all of the family. There has never been any letting. No elections of any kind have been made but a declaration of trust has just been found. The parents signed a declaration of trust at the time of the purchase transferring 90% of the value of the property equally to the four children which I assume means that the individual base cost for each became £16 875.

The father died in July 2007 at which time the property was valued at £300 000 meaning his 5% share at that time would have been worth...