take into account (i) any advantage to the plaintiff; (ii) any disadvantage to the defendant; this is the critical equation, and in some cases it will be a difficult one to establish. Generally this is done by an instinctive process - that is what discretion, in its essence, is.
He added [9] :
I think too that there must be a relative element in assessing both advantage and disadvantage - relative to the individual circumstances of the plaintiff and defendant.
Once the inquiry became a balancing exercise, it was impossible to maintain the formulation of Scott L.J. as the guiding principle, as Lord Diplock pointed out in MacShannon v. Rockware Glass Ltd. [10] . He restated Scott L.J.'s formula [11] so as to compare the convenience and expense of trials in the available fora and so as to preserve for a plaintiff "a legitimate personal or juridical advantage". Lord Diplock's restatement proved to be an inadequate bank to hold back the tide of a broad, virtually unstructured discretion. Lord Salmon said [12] :
To my mind, the real test of stay or no stay depends upon what the court in its discretion considers that justice demands. I prefer this test to the test of whether the plaintiff has behaved "vexatiously" or "oppressively" on a so-called liberal interpretation of these words. I do not, with respect, believe that it is possible to interpret them liberally without emasculating them and completely destroying their true meaning.
Lord Fraser of Tullybelton adopted the test whether a stay would produce injustice but thought that that question could be answered "generally" by Lord Diplock's restatement [13] . Lord Russell of Killowen thought that the result of MacShannon was to stop "not far short of balance of convenience" [14] . Lord Keith of Kinkel developed two further notions: the notion of a "natural forum" and the notion of injustice consisting in a serious, outweighing disadvantage. He said [15] :
Where England is the natural forum for the action, in the sense of being that with which the action has the most real and substantial connection, it is necessary for the defendant, in order to establish injustice to him and no injustice to the plaintiff, to show some very serious disadvantage to him which substantially outweighs any advantage to the plaintiff. Where, however, the defendant shows that England is not the natural forum and that if the action were continued there he would be involved in substantial (i.e., more than de minimis) inconvenience and unnecessary expense, or in some other disadvantages, which would not affect him in the natural forum, he has made out a prima facie case for a stay, and if nothing follows it may properly be granted. The plaintiff may, however, seek to show some reasonable justification for his choice of forum in the shape of advantage to him. If he succeeds it becomes necessary to weigh against each other the advantages to the plaintiff and the disadvantages to the defendant, and a stay will not be granted unless the court concludes that to refuse it would involve injustice to the defendant and [the grant would involve] no injustice to the plaintiff. As to the nature of the advantages and disadvantages which may go into the scale on either side I am of opinion that they must be such as are capable of being objectively demonstrated.
In The "Abidin Daver" [16] Lord Brandon of Oakbrook pointed out that a defendant no longer had to satisfy the court that continuance of the action would be oppressive or vexatious to him:
[T]he exercise of the court's discretion in any particular case necessarily involves the balancing of all the relevant factors on either side, those favouring the grant of a stay on the one hand, and those militating against it on the other. Such balancing may be a difficult process and some cases may be very near the line.
In that case, Lord Diplock [17] thought the time had come to acknowledge that the English law was "indistinguishable from the Scottish legal doctrine of forum non conveniens" - the doctrine which had been rejected in The "Atlantic Star" [18] .
1. [1974] A.C., at p. 454.
2. [1974] A.C., at pp. 464, 468.
3. [1974] A.C., at p. 475.
4. [1974] A.C., at p. 468.
5. [1974] A.C., at p. 469.
6. [1978] A.C. 795, at p. 811.
7. [1978] A.C., at p. 812.
8. [1978] A.C., at p. 819.
9. [1978] A.C., at p. 822.
10. [1978] A.C., at p. 823.
11. [1978] A.C., at p. 829.
12. [1984] A.C. 398, at p. 419.
13. [1984] A.C., at p. 411.
14. [1974] A.C. 436.