For me, Lord Bingham's most important contribution was to settle a debate about the status of an accused person's right to a fair hearing. While some judges were prepared to see this as a right that could be qualified by being balanced against the rights of the prosecution and of victims, in Randall v R (Cayman Islands)  UKPC 19 at para 28 Lord Bingham, for the Board, established the absolutist position:
But Lord Steyn had delivered the Board's judgment in Mohammed v The State (Trinidad and Tobago)  UKPC 49 (9 December 1998), saying at para 29 "a breach of a defendant's constitutional right to a fair trial must inevitably result in the conviction being quashed." Is there a problem? Was Lord Steyn suggesting a model of fairness where whatever "fair" means, it is absolute, but its meaning is determined by triangulation? That possibility is excluded by H, triangulation is confined to other rights and its results are subject to the test of fairness (see para 36, step 6). Were it to be otherwise, "absolute" would mean nothing. To borrow Larkin's apposite phrase, "one side will have to go".
The accepted position is summarised in  New Zealand Law Review 217 at 249 (footnotes omitted):
"The question is not how unfair is the accused’s trial required to be because of proper restrictions on cross-examination, but rather, what restrictions on cross-examination are compatible with the accused’s absolute right to a fair trial? Again, the question is not to what extent may reasonable breaches in identification procedures limit the accused’s right to a fair trial, but rather, what failings in identification procedure are compatible with the accused’s absolute right to a fair trial? The question is not to what extent may disparities in the opportunity of expert witnesses to examine the relevant evidence limit the accused’s right to a fair trial, but rather, what disparities are compatible with the accused’s absolute right to a fair trial? The question is not, to what extent may pre-trial publicity limit the accused’s right to a fair trial, but rather, what level of publicity is compatible with the accused’s absolute right to a fair trial? The question is not, to what extent may breaches in the rights relating to police questioning be allowed to limit the accused’s right to a fair trial, but rather, what departures are consistent with both the accused’s right to a fair trial and wider issues of prevention of abuse of process?"
Eight days before Condon was decided, no less a legal scholar than Grant Hammond (who has achieved praise in these blogs) delivered a lecture in which he said (p 20) "The question whether it is possible to have an unfair trial but a safe conviction is maddeningly simple. But there is no clear answer" and he favoured a broad approach whereby if a conviction appeared safe on the evidence at trial, the accused's appeal should only be allowed on unfairness grounds if a balancing of rights supported that conclusion. What was clear to Lord Bingham might only slowly become apparent to others.
In New Zealand we have particular reason to remember Lord Bingham as the judge who delivered the devastating rejection of the Court of Appeal's analysis of the case against David Bain: Bain v R (New Zealand)  UKPC 4 (16 March 2009). Applying the correct approach to the proviso, the Board ordered a new trial. Mr Bain (as all New Zealanders know) was subsequently acquitted of the murders of his parents and three siblings. The New Zealand courts have now changed their approach to the proviso, although the Privy Council insists that the result in Bain would have been the same: Barlow v R (New Zealand)  UKPC 30, para 21.