Legal quiz: could you handle a reverse ambush?

You've been appointed adjudicator in a dispute under a JCT 98 contract.

A quick look through the contractor's referral reveals there's nothing unusual in the claim - a valuation dispute with an employer, a little bit of delay and disruption, no withholding notice, no legal or design arguments. You're a quantity surveyor, easy you think.

Appended to the response you're delighted to see an engineer's report dealing with defects and specification anomalies, a planner's report detailing programme issues and a quantity surveyor's report valuing the works based on the other two experts' reports. All the reports have been prepared after your appointment. The valuations are far apart.

Before long the fax machine starts smoking.

The contractor's correspondence is sprinkled with "not seen before", "ignore this new expert evidence" and "reverse ambush", which you quite admire as a phrase; as usual "outraged" appears to make more than a few appearances. Despite wishing you to ignore the reports, the contractor also makes a few brief general comments on them.

The employer insists that it is able to defend itself by whatever means it chooses and that to ignore the material would be a gross betrayal of natural justice.

Case law has been presented for you to consider and the arguments simmer on.

Neither party raises the issue of extending the time in which you have to make your decision and you decide, in any event, to deal with the matter.

In your decision as the adjudicator, how do you deal with the introduction of the new evidence in the experts' reports?