Can you be taxed on a house you won in a lottery?

A friend of mine won a house in a lottery, Now he is been hit with a massive tax bill based on inheritance tax. I know its a great win and its not much to pay for a free house but what I'm thinking is if you won money,car,holiday etc on lottery programs its stated its tax free, If you won on the horses its tax free, so why is this taxable or does anyone know, and just in case they make a mistake they tax him anyway, Is it one law for some winners and another for the others,
Thank you for your views.

I think that the lotto etc may be tax free because they are charities. Private lotteries may not be exempt. That is only a hunch though.

The reason normally given for the non taxing of gambling winnings is that gambling losses are not tax deductible. In this case perhaps the revenue feel the whole thing was a sham (rather like the taoiseach's digout 'loans') and so are applying CAT rules?