By custom, however, he or she does so only in exceptional circumstances.

In some exceptional circumstances, it may be appropriate to do both.

Other methods are possible - but only in exceptional circumstances.

Under exceptional circumstances, it is possible to score a break of 155.

In exceptional circumstances, this may mean having to tell you about the death over the phone.

Such financial assistance should only be necessary in the most exceptional circumstances.

Some or all of these rights may be suspended in exceptional circumstances.

But it must only be used in the most exceptional circumstances.

This may be extended to two years in exceptional circumstances.

You seemed to say that it would only be in very exceptional circumstances.