Clair Allison was caught on camera exceeding a temporary 40mph limit in roadworks on the A303 at Folly Bottom.

She challenged the prosecution using photographic evidence and a report from a sign expert.

The case was dismissed by Salisbury Magistrates' Court because of a lack of evidence from the Crown Prosecution Service.

The CPS added that it has "decided to withdraw [further] speeding prosecutions" for the period the roadworks were in place.

A statement said that the defence report highlighted there was not a "high standard of checks to ensure that the signage met legal requirements".

'Doubts raised'

A statement from the Wiltshire and Swindon Safety Camera Partnership said: "The Crown Prosecution Service has confirmed that there was clear evidence of careful checks of the signage having been carried out by police officers conducting enforcement.

"But a doubt was raised due to the fact that contractors' written records were not available during the early stages."

Ms Allison, a make-up artist, said: "At that point it is a 70mph limit and I didn't see any signing so that was what threw me completely.

"I think the safety camera has a lot to answer for. I think it has huge implications for people all over the country."