I'm assuming this is going to end up in front of a judge?

A set of forensic questions put to the vendor in front of the judge should focus the defendants mind. Also possibly a witness summons for the engineer who prepared the report. Dodgy paperwork is one thing; perjory is another.

It's probably the dealer pulling the last few things out of the hat hoping you will cave in and give up..........so, call his bluff and continue, most people like that try these sort of bullying tactics and generally get away with it, keep the pressure on and you will most likely win in court, or he will settle out of court just beforehand.

>> the court, the police and trading standards and they all agree that the document looks suspicious.

Get as many of 'em as you can to make a statement to that effect.

And if it turns out to be genuine?

No, I doubt you'll be able to get any of 'em to make a statement, too risky.

I doubt that police would make any sort of "statement" as to the provenance or otherwise of an engineering report-unless of course it was proven to be fraudulent.

They are just not going to put "It looks dodgy" in writing.