Had to go through one recently to get to a garden centre, and checked on the net after about it and found this.
Nice bit of road that is… in a car or on a bike that is… reckon its a tad tight in a artic 
I reckon they need to change all the old 17t limits to 18t now because the idea was to limit access to rigid vehicles which have more than two axles
For any new signs installed the goods vehicle limit can either be 7.5t or 18t and the weight limit applying to all vehicles can be 3t, 7.5t, 13t, 18t, 26t or 33t.
legislation.gov.uk/uksi/2011 … 041_en_010
I don’t think that makes any older limits invalid, as the legal orders which make the limit enforceable would need to be changed if the signs were to change to one of the new options.
The 1994 regulations allowed 3T, 7.5T, 10T, 13T, 17T, 25T and 33T.
legislation.gov.uk/uksi/1994 … 519_en_041
But any very old signs with imperial weights or axle weights would unlikely to be enforceable as there is nothing like them in current regs or the Highway code etc. And your plating certificate doesn’t state how many hundredweights your vehicle is, anyway!
Swampey2418:
Nice bit of road that is… in a car or on a bike that is… reckon its a tad tight in a artic
It’s do-able if you utilise the passing places. 
Grow a pair and move…
for ■■■■ sKd…
you are a truck driver…