Dear Helen
You are absolutely right - a great deal depends, not only on the severity of the illness, but on an individual's ability to cope with it. It is known to skip generations and there is a number of precipitants, e.g. a change of diet, or through use of certain drugs. Alchohol is a major contributor.
I brought up the topic of Princess Margaret and porphyria in response to Martyn's question after discovering it was Princess Margaret's own biographer, James Brough, who raised the possibility of her suffering from porphyria. It would be interesting to know the identity of your own 'reliable source'. I think it unlikely she suffered from porphyria. This is an uninformed opinion.
Porphyria is a horrible disease manifested by many and various symptoms. I am sure you will agree it should not be dismissed as just 'feeling under the weather' and is in no way amusing. Sufferers are frequently labelled as hypochondriacs which is cruel in the extreme, since, in its severest form, it is extremely distressing and dibilitating both for the victim and for their carer.
tsaria