The 70 mph National Speed Limit was introduced as a temporary measure in December 1965. It is often blamed on Barbara Castle, 
but at the time the Minister of Transport was Tom Fraser.
The reason given was a spate of serious accidents in foggy conditions, but it is often claimed that the MoT had been alarmed by AC Cars testing their latest Cobra on the M1 at speeds up to 180 mph. 
It was confirmed as a permanent limit in 1967, by which time Barbara Castle (a non-driver) had become Minister of Transport.There was surprisingly little debate at the time: the fact that the average family car of the time could only just exceed 70 mph perhaps had something to do with this.
It should be noted that this limit applied to all previously āderestrictedā roads, not only motorways. 
The black Dafs were John Macdonald airfrieght who were based at Glasgow Airport, the other DAF out of Glasgow at night was Nightfreights 3300 close coupled top sleeper which did glasgow/liverpool/willenhall/Liverpool/Glasgow double manned and nothing could catch it, was driven by the Clocherty brothers of Renfrew
TIR Original:
[Stepthru, I think the realistic speeds have all been covered in this thread and through over 45 years of HGV driving experience I can vouch for them as being feasible.
Nevertheless I would not like you or any other younger drivers to be mis-lead about past speed laws as regards to heavy lorries. Since the very first stretch of the M 1 was open in 1959, the maximum speed limit for HGVās has only ever been 60 mph. HGVās have never ever been permitted to use the third lane. This was only ever permitted by 7.5 tonners and even a tractor unit could ever use the third lane if it was not fitted with a fifth-wheel and not capable of pulling a trailer. I really do not wish to deliberately undermine anybody or offend but also I would not wish to see anyone mis-lead.
Well, Iāll limit myself for the time being to āI disagreeā and if I ever get the time to research the subject, Iāll quote chapter and verse. 
Thanks for that Willie-Mac ā¦spot on with John Macdonalds
Got to know a few of the drivers they sometimes parked there Units on a Saturday night in a local Pub/ Night club in Slough called sluffs (or Cruffs as we all called ).LOL.
Do you think you could get away with that now days.
Night clubbing till 2am walk out to the car park over night in cab get up sunday and have Sunday lunch in the pub. 
Must have made the 24 hours off better than going home LOL.
In 1969 i drove a scammel handyman with a leyland 680 fitted under the bonnet,it had the exhaust coming out in front of the first axle and at night you could wind it up on the m6 and watch a blue flame coming out the pipe.I got followed by the old bill in a jag on the A66 and got done at kendel court 35 quid for travelling at 79mph over a distance of 3 tenths of a mile.
16speed F88 , 32ton up , 85mph , crazy when i look back , but thats what we did in those days ,
interesting replies chaps ā no way Iād be going at some of those speeds in those old rattlers!
I remember get a lift from a Tolley & Smales wagon one day when I was having a ādodgyā in Bristol. He had a full load on and knocked it into Cornish Overdrive going down Redhill (A38 south of Bristol - 1 & a half miles long!) I donāt know what speed we got up to I, was too busy cr****ing myself to look at the speedo, but we only just made the bend by the Paradise Motel near the bottom.
Had a Seddon atki 400 with 290 ā ā ā ā ā ā ā would do 70 uphill and down dale also had 111 that would do 75 over scamoden on the 62 oh to be young and fearless or stupid not sure which. but lot less traffic then my excuse anyway
mr big:
In 1969 i drove a scammel handyman with a leyland 680 fitted under the bonnet,it had the exhaust coming out in front of the first axle and at night you could wind it up on the m6 and watch a blue flame coming out the pipe.I got followed by the old bill in a jag on the A66 and got done at kendel court 35 quid for travelling at 79mph over a distance of 3 tenths of a mile.
And iāve been picked up by that truck iām sure when on the occasional dodgy.
I think i worked with āTaffyā some years ago on tippers and iām sure he drove that truck at some point, possibly also Paul Holloway from Irthlingborough (ex Clarks like me). Jog any memories?
Early 70ās run night truck Bathgate to Ipswich, Geest container, down loaded with Whisky, back loaded with Dutch Ham. Wagon was Atki borderer 180 Gardner engine twin speed Diff.
Boss clocked me doing 85 MPH on A74, Speedo stopped at 60.
In those days, no duel carriageway from A1 to Ipswich, had to go through all Towns & villageās on A45.
Still managed to complete run in under 10 hours, now who knows, how long.
I was running with my mate on fallen timber clearing Boxhill about 1988/9. I had an old knacker of a 140 and he had a Transcon. We loaded and headed for the motorway near Dorking. We got split up and hadnāt decided on a route home to East Yorkshire.
I went up the M1 trying to catch him, he had gone up the A1 thinking I was in front of him 
I think the police and advanced motorists call it āmaking progressā Anyway 3 hours 20 minutes later Im in the yard waiting for him as he pulled in 15 minutes later 
It was a clear run and the roads were a bit clearer.
davemackie:
Early 70ās run night truck Bathgate to Ipswich, Geest container, down loaded with Whisky, back loaded with Dutch Ham. Wagon was Atki borderer 180 Gardner engine twin speed Diff.
Boss clocked me doing 85 MPH on A74, Speedo stopped at 60.
In those days, no duel carriageway from A1 to Ipswich, had to go through all Towns & villageās on A45.
Still managed to complete run in under 10 hours, now who knows, how long.
you do mean one way dont you ? 
Juddian:
mr big:
In 1969 i drove a scammel handyman with a leyland 680 fitted under the bonnet,it had the exhaust coming out in front of the first axle and at night you could wind it up on the m6 and watch a blue flame coming out the pipe.I got followed by the old bill in a jag on the A66 and got done at kendel court 35 quid for travelling at 79mph over a distance of 3 tenths of a mile.And iāve been picked up by that truck iām sure when on the occasional dodgy.
I think i worked with āTaffyā some years ago on tippers and iām sure he drove that truck at some point, possibly also Paul Holloway from Irthlingborough (ex Clarks like me). Jog any memories?
hey brian would that be taffy jones from higham by any chance?
steve.
early 80s would leave wellingborough at 5am and be in crawley nr gatwick by 06.55am, 1hr 55mins every time. that was in a leyland buffalo and going straight through the smoke via vauxhall bridge!
steve
Had a 1735 merc (of course) lit it up on the motorway at Chamberey one night & it went so fast that the mirrors blew back against the doors 
My mate followed me up the A2 in his car when I was solo & it did 3 digits, liked a drop of squirt though 
newmercman:
Had a 1735 merc (of course) lit it up on the motorway at Chamberey one night & it went so fast that the mirrors blew back against the doorsi was with newmercman that day and boy did that make us 2 jump when they folded in with a big bang and do you remember going round that slip road and sliding off your seat because of the speed you was doing.
and talking of going fast how about you following me down the M1 in your car with me off the clock do made in sweden speed in the old 530.
newmercman:
Had a 1735 merc (of course) lit it up on the motorway at Chamberey one night & it went so fast that the mirrors blew back against the doors
did the same thing in a 1633, took up all the slack in the throttle linkage, did she go or what, and then when you floored the pedal to hit the power button it was like warp speed!!
so come on mercman get over to canada, we aināt got limiters yet and hardly any speed cameras!!!
steve.
STEVE OWEN:
newmercman:
Had a 1735 merc (of course) lit it up on the motorway at Chamberey one night & it went so fast that the mirrors blew back against the doorsdid the same thing in a 1633, took up all the slack in the throttle linkage, did she go or what, and then when you floored the pedal to hit the power button it was like warp speed!!
so come on mercman get over to canada, we aināt got limiters yet and hardly any speed cameras!!!
steve.
Pull your mirrors in mate, Iām on me way, should be there by the end of the month 
davefluffy:
newmercman:
Had a 1735 merc (of course) lit it up on the motorway at Chamberey one night & it went so fast that the mirrors blew back against the doorsi was with newmercman that day and boy did that make us 2 jump when they folded in with a big bang and do you remember going round that slip road and sliding off your seat because of the speed you was doing.
and talking of going fast how about you following me down the M1 in your car with me off the clock do made in sweden speed in the old 530.
Yo Fluffy, your memory aināt so good, I slid off my seat going up to the Tunnel du chat, it was on that right hander before the fish resturaunt at the bottom of the hill, mind you it probably cos you had your eyes shut
They were quick motors but I reckon your 42 Turbostar wouldāve done em both, then again my 48 Turbostar was quicker still & boy did that baby roar through them Eminox 
Talking about belting down the M1, do you remember when I bought that 520 Eurostar in Burton & come down solo, somehow the fuse fell out that thing could shift, Iām still paying the diesel bills for that now