I'd imagine that travel in Europe, even pre-Schengen, (not Eastern-bloc of course) was probably fairly easy anyway with porous borders that are fairly impossible to police.
That's a fascinating insight into biometric passports - matching the details on the chip to the details on the page - and not much else - serves a purpose I suppose.
Back in the early to mid 90s I had a job which involved sending documents with legal standing - we only used faxes for fast transmission because email transfers didn't exist and there were no scanners to upload the documents anyway, even if it had existed.
Of course, the technology probably existed in Silicon Valley and Universities but not for ordinary usage.
As you say, the UK isn't (never has been?) signed up to Schengen so free movement not as free as in other countries but in the last 35 years I've walked past as many unmanned (probably more) as manned passport desks - I can recall my passport being physically handled and read twice but never copied or scanned.
I doubt there's any obligation on airlines to keep passenger lists or that long or credit card records.
Different world then - they hadn't invented small data storage so they edited for likely future value and discarded the rest - shame the BBC did that with all their old recordings too.
Did the teacher/prostitute have a flashback of the murder victim? Or was it just a general flashback?
I'm speculating on a wild party at the lawyer's London pad with drugs and prostitutes and wealthy Tory donors...