What CGT liability for property that is partly PPR?

Please could you tell me what capital gains tax (CGT) each party would pay if there was a 50/50 ownership at sale, but it was one of the owner’s primary residence?

Arthur Says

If A and B own a property 50:50, then the sale proceeds and the base cost of the property are divided in two, and two separate CGT calculations are made, one for A and one for B.

If it is A's principle private residence, then A will be exempt from any CGT, but B will be liable in the normal way on B's half.

This kind of scenario can occur in a divorce situation, when A stays in the property, and B moves out.

Some time later the property is sold, but since moving out it is no longer B's PPR. The last three years of ownership of B will be deemed to be occupied and therefore eligible for PPR relief, because previously B actually occupied the property.

The Revenue Extra Statutory Concession D6 may be relevant here.