The helicopter in the crash is a 15-seat medium sized twin-engined helicopter manufactured by Italian company AgustaWestland - and one of the men who died had previously lodged a claim against its makers.

Conservative peer Lord Ballyedmond who was killed in a helicopter crash last night had recently raised safety concerns with the aircraft's manufacturers.

Lord Ballyedmond, one of the richest men in Northern Ireland, was chairman of Norbrook, the largest privately owned pharmaceutical company in the world.

His AgustaWestland AW139 helicopter came down in thick fog in a field in Gillingham, near Beccles, Norfolk, at 7.30pm yesterday killing him and three others.

It has now emerged that his company Haughey Air Ltd had lodged a writ against AgustaWestland over concerns about a helicopter supplied by them.

The case was lodged in September last year and is understood to have included concerns about in-flight mapping systems.

A spokesman for AgustaWestland said it could not comment on possible defects with Lord Ballyedmond's AW139 VIP helicopter but said it was investigating.

Speaking from the company's office in Italy, he said: 'We cannot comment now because we need to make internal checks to establish exactly what the situation is.

'We cannot yet comment on this accident because there is an investigation pending and there could be many causes, be them technical or due to human error.

'Obviously we are very much regretful of what happened and will support the ongoing investigation in any possible way.'

In February 2012 an inquest heard in-flight technology systems on board AgustaWestland helicopters should be improved after a crash which killed a friend of the Prince of Wales.

The mapping databases display the height of terrain like mountains and whether certain areas are available to fly through but the four-day inquest in Belfast highlighted flaws.

The aircraft flew into the side of a cloud-shrouded mountain in the Mourne range, Co Down, in October 2010 as it carried a shooting party back to England.

The probe into the death of three people, including the Prince's friend Charles Stisted, heard how land above a certain height was not displayed and a prohibition on flying through South Armagh still showed although it was lifted several years earlier.

Construction company businessman and fellow polo player Ian Wooldridge, 52, and experienced pilot Anthony Smith, 63, formerly of the RAF and Army with service in Northern Ireland, also died.

Known as Edward Haughey until he was made a life peer in 2004, Lord Ballyedmond owned Gillingham Hall, a stately home near the crash site, according to the Register of Lords' Interests.

The Westland AW139 was originally designed and developed jointly by Agusta and Bell Helicopters and marketed as the Agusta-Bell AB139.

In 1997, the manufacturer launched a programme to develop a replacement for the Bell Huey family of helicopters with a potential market of 900 aircraft being predicted.

On 26 September 2000, the first order for the type was placed by Bristow Helicopters.

It is described by its maker as 'a new generation medium twin-turbine helicopter setting new standards against which all medium twins are measured'.

The AW139 is used by both private individuals and companies and helicopter charter, including offshore support. It is also used by law enforcement and government use in particular air ambulance and coastguard use.

KEY CHARACTERISTICS

Crew: 1 to 2

Capacity: 15 passengers

Length: 13.77m

Main rotor diameter: 13.80m

Width: 2.26m

Height: 3.72m