Extraordinary video footage of HS2 night-shift workers firing a powerful air rifle inside a workshop led to a police investigation, The Mail on Sunday can reveal.

Five workers were sacked from the £100billion rail project after a whistleblower came forward with allegations concerning the ‘dangerous and unethical’ behaviour of his colleagues.

Footage captured by Aminadab Enos de Souza Dias, 42, showed mechanics at HS2’s construction site in West Ruislip, London, whiling away the early hours blasting targets with an air rifle while listening to heavy metal music.

Mr Dias, a fitter’s mate from Brazil, also submitted a dossier of maintenance and safety concerns, including photographs of his colleagues asleep on the job, and alleged he was subjected to ‘verbal abuse, xenophobic comments and intimidation’.

The Government ordered an investigation after Mr Dias emailed the then Prime Minister Sir Keir Starmer to warn him that the gun had been smuggled into the West Ruislip site, where an 8.4-mile tunnel is being dug.

Separately, the MoS has learnt that an explosion took place at the same site seven months earlier in 2024.

CCTV footage obtained by this newspaper shows workers wearing bright orange jackets hit by a powerful blast as they attempted to fix a leaking cement pipe. Four went to hospital, although HS2 said there were no ‘major injuries’.

The revelations throw the spotlight back on a beleaguered project that has become synonymous with colossal waste and delay.

Extraordinary video footage of HS2 night-shift workers firing a powerful air rifle inside a workshop led to a police investigation

Photographs also showed HS2 workers asleep on the job at a construction site in West Ruislip, London

Whistleblower Aminadab Enos de Souza Dias, 42, came forward with allegations concerning the ‘dangerous and unethical’ behaviour of his colleagues

HS2’s cost has ballooned from £37.5billion in 2009 to potentially more than £100billion, with services not reaching central London until 2040 at the earliest.

Mr Dias claims the air rifle – owned by mechanic Keith Mewes – was kept at the site for more than two months in the spring of 2025. 

He said the gun was ‘frequently’ used on site, adding: ‘I left Brazil looking for a safer and better life. Ironically, I was forced to return.’

Videos recorded by the fitter’s mate show Mr Mewes and a second man firing the gun, which appears to be a .22 calibre Stoeger X20 S2, inside the workshop.

Mr Dias alerted HS2 and its contractor SCS in May 2025 but, after becoming frustrated at their response, contacted Downing Street in October. 

His email was forwarded to Lord Hendy, the Rail Minister, who said he was ‘shocked’ at Mr Dias’s complaint and had personally raised it with HS2 boss Mark Wild.

In a letter to Mr Dias, Lord Hendy revealed that one worker had been dismissed and ‘four other individuals involved in the incident have been removed from HS2 work immediately and permanently’.

Mr Mewes, the dismissed employee, told the MoS he took his gun to work to repair it during his breaks, but accepted this was ‘inappropriate’, adding: ‘I deeply regret the decisions I made.’

It’s claimed the air rifle – owned by mechanic Keith Mewes – was kept at the site for more than two months in the spring of 2025.

British Transport Police said it launched an investigation but its probe was closed after ‘it was established that the suspected air rifle was no longer on site’

It appears the rifle kept at the workshop was a Stoeger X20 S2 Suppressor Combo Air Rifle (pictured)

British Transport Police said it launched an investigation but its probe was closed after ‘it was established that the suspected air rifle was no longer on site’.

A spokesman for HS2 said: ‘This was an unacceptable and isolated incident that took place around 18 months ago and action was taken to dismiss individuals involved and overhaul health and safety processes on sites to ensure this couldn’t happen again.’

It added that changes had been made to SCS’s leadership, and searches for prohibited items had increased.

Meanwhile, it is understood the explosion in 2024 was caused by a compressed air line.

HS2 said: ‘We took a number of actions to rectify the issues identified and improve safety.’