A stretch of motorway most drivers treat as routine became something rather more serious last December, when a heavy goods vehicle was stopped near Swindon.
Now, months later, the consequences have caught up.
Wiltshire Police confirmed that John James Withey, 44, of Northampton, appeared before Swindon Magistrates Court on 16 April, where he admitted to drug driving.
The offence dates back to 18 December 2025, when a roads policing officer spotted Withey driving an articulated lorry along the M4 motorway between junctions 16 and 15. He was directed off the motorway and stopped at the DVSA weighbridge at junction 15, where a roadside drugs test returned a positive result for cannabis.
Further analysis showed he was nearly twice the legal limit.
It’s the sort of detail that carries more weight given the vehicle involved. Driving under the influence is risky enough in any car, but an HGV brings with it a different scale of consequence—greater mass, longer stopping distances, and far less margin for error.
Police were clear on that point. Officers said impairment behind the wheel of such a vehicle significantly increases the danger to other road users, particularly on busy routes like the M4.
Withey has now been disqualified from driving for 17 months and fined £750. He must also pay a £300 surcharge and £85 in costs.
Cases like this tend not to attract much attention beyond the courtroom, but they form part of a broader effort to tackle drug driving on Wiltshire’s roads. Enforcement has become more visible in recent years, with roadside testing now a routine part of traffic stops where impairment is suspected.
For most motorists, it’s a reminder rather than a revelation. The rules are well known. The risks, even more so.
And on roads as busy as the M4, it doesn’t take much for a lapse in judgement to become something far more serious.
