Tax?

So I saved a 1995 discovery 300tdi from the scrap pile a couple of months ago and I've now got free time so she has no number plates but I found the service book with the chassis code and Registration plate and decided to search gov.uk to see when it was last taxed to find out its taxed ran out in 1999 the service book also has 9 services filled in up unto this point and has 40k miles wrote down and it now has 170k miles so how was this registered to be on the road? Surely it wasn't just used solely on a farm for over 130k miles?

Could it have had a change of number plate in '99?

As above e.g. personal plate

Has it got a V5, if you got it from a scrap yard, it may have been had the V5 marked as scraped.