We start in the Court of Appeal in Armagas Ltd v Mundogas S.A. (the “Ocean Frost”)  Vol. 1 Lloyd’s Rep.1.
At page 57 Lord Goff said,
Speaking from my own experience, I have found it essential in cases of fraud, when considering the credibility of witnesses, always to test their veracity by reference to the objective facts proved independently of their testimony, in particular by reference to the documents in the case, and also to pay particular regard to their motives and to the overall probabilities. It is frequently very difficult to tell whether a witness is telling the truth or not; and where there is a conflict of evidence such as there was in the present case, reference to the objective facts and documents, to the witnesses’ motives, and to the overall probabilities, can be of very great assistance to a Judge in ascertaining the truth.
From there we move to the Privy Council.
In Grace Shipping Inc v C. F. Sharp & Co. (Malaya) Pte. Ltd  Vol. 1 Lloyd’s Rep.207 giving the decision of the Privy Council Lord Goff went said pages 215/16,
And it is not to be forgotten that, in the present case, the Judge was faced with the task of assessing the evidence of witnesses about telephone conversations which had taken place over five years before. In such a case, memories may very well be unreliable; and it is of crucial importance for the Judge to have regard to the contemporary documents and to the overall probabilities.
After approving the approach outlined in the Ocean Frost, Lord Goff went on to say ,
That observation is, in their Lordships’ opinion, equally apposite in a case where the evidence of the witnesses is likely to be unreliable; and it is to be remembered that in commercial cases, such as the present, there is usually a substantial body of contemporary documentary evidence.
You will find these cases cited in Synclair v East Lancashire Hospitals NHS Trust  EWCA Civ 1283.