You need to measure yer size 12's and be comparative to estimate the tail, without telling us fishermans tales!!
How big was it in new or old money??
I shoot and trap loads on farms each year some of which are a fair size.
Now, i have seen bigger rats than i have ever shot or trapped but the biggest i have ever accurately measured was around the 19" mark, (with photos to back it up).
I think there was a 21" on here last year.
Did you find the rat?? Poisoned? or did YOU trap or shoot it??
If you cant accurately tell us the size, then how does anybody know if they can be