Russell Leggett, from Bassett, and Robert Peach, from Hamble-le-Rice, required hospital treatment after inhaling dust and fumes when steel coated in lead paint was cut into and removed from the structure in July 2013.

Blood tests showed traces of lead far exceeded safe levels – and was almost double the acceptable standard in Leggett’s case.

Both workers required intensive treatment and months of monitoring before their blood tests returned to safe levels.

Bam Nuttall and Four Tees Engineering Ltd were prosecuted after an investigation by the HSE identified failings with control measures surrounding the steel cutting work.

Portsmouth Crown Court heard that Bam Nuttall was responsible for a project to remove weathered steel from the Nab Tower – a former military control installation that has become an important beacon for captains navigating the busy waters around the Isle of Wight and the Solent.

The work involved removing sections of steel using industrial torches, a job that was subcontracted to Four Tees, with workers from both companies involved.

Despite knowing the steel was coated in lead paint, Bam failed to apply this knowledge and assess the need for control measures against lead exposure.

HSE established that Four Tees was equally culpable because it too overlooked suitable control measures, and also failed to ensure its employees had suitable medical surveillance whilst working with a potentially harmful substance.

Leggett and Peach, whose blood tested positive, were both employed by Four Tees. Three Bam Nuttall workers were also exposed and put at risk, although their tests proved inconclusive.

After the incident, strict rules were implemented to create ‘clean’ and ‘dirty’ areas where decontamination was required before transferring from one to the other.

Workers were also given better face masks and regular medical surveillance.

Bam Nuttall, of Camberley, Surrey, was fined a total of £56,000 and ordered to pay £6,165 in costs after pleading guilty to safety breaches.

Four Tees Engineering Ltd, of Fareham, was fined £14,000 with £2,081 costs.

After the hearing, HSE inspector Andrew Moore said: “The Nab Tower exposure was serious, and demonstrates the need to properly assess and guard against potential inhalation of lead fumes and dust.

“The paint coating the steel was known to contain lead and it should have been handled with care from day one. Instead both companies allowed a number of unsafe practices, including eating, drinking and smoking, to continue unchallenged at the site that fuelled potential contamination.

“Not that the workers would have known because there was no surveillance in place to monitor levels of lead in their blood and flag when the exposure had occurred.

“Duty holders should always err on the side of caution when cutting, stripping or grinding painted material and assume it contains lead unless there is good evidence to prove otherwise. That means having adequate decontamination, surveillance and other control measures in place.”