Hi,
I don't want to be giving unduly cryptic answers, and this is certainly not about keeping information out of public readership, but some tax issues are quite complex and can be particular to the circumstances of each case. I have devised one brilliant (though I do say so myself) avoidance strategy which I have been unable to use for years because I haven't yet had a client whose circumstances fitted the strategy. (yes, I know, I should get out more). If I start giving examples of relatively complex tax planning strategies, I would be mildly concerned that someone else reading this might try to rely on what I say instead of getting the proper advice.
The important thing is that your father's solicitor knows to seek advice from a specialist. If he doesn't know who to refer the matter to, feel free to PM me. While I cannot take this on myself, I can certainly give you some names for your father's solicitor.