[1] IRN launched on 8 October 1973, with the first bulletin read at 06:00 by Australian newsreader Ken Guy on the opening morning of Britain's first commercial radio station, LBC.
IRN was based at LBC studios in Gough Square, just off Fleet Street in Central London.
In 1989, satellite distribution of bulletins and audio was introduced, and this was also the year that IRN and LBC moved into new studios on Hammersmith Road in West London.
All IRN branding was removed, and the outcue reverted to a time check: "It's three minutes past [the hour]."
A shorter 90-second bulletin, known as IRN 90, was introduced on the IRN2 channel comprising stories aimed at younger, pop music stations.
In June 2008, IRN started supplying a feed of news, sport and entertainment stories and video to the websites of client radio stations.
Bulletins were broadcast 24 hours a day from Chiltern studios in Dunstable utilising audio from Sky News and CNN Radio.
Reuters Radio News ran from 1994 until June 1996 from studios at Gray's Inn Road in London.
BSkyB launched Sky News Radio in June 1999 as a rival to the ITN-operated IRN service.
It initially provided bulletins to Talksport and subsequently around eighty radio stations before taking over the IRN contract in March 2009.
Thirty-second, three-minute and five-minute bulletins are distributed via FTP to clients including digital, community and online stations.
Many stations take the national IRN bulletin during evenings and weekends when local newsrooms are unstaffed.
A two-minute recorded bulletin is offered during off-peak periods which is distributed to stations just before the top of the hour.
Most client stations have blue "obit lights" installed in their studios which are automatically triggered by IRN in the event of the death of a member of the Royal Family or other major national (and in some cases international) figure.
Formerly, there was a strictly defined protocol for such occasions that all ILR stations were required to follow which included suspending normal programming and advertising.
The IRN network channel would then switch to special programming which consisted of light instrumental music and announcements every ten minutes, with extended news bulletins on the hour and half-hour.
[7] Over time, however, the status of the obituary protocol has declined to the point where there is no longer any statutory instruction, obligation or procedure defined anywhere, either in the Ofcom code nor any station's licence.
It is generally accepted that broadcasters will adopt a suitable tone of some kind, but there is no formal requirement for them to do so, and the nature of any obituary response is entirely down to the individual stations.
Although there is no formal obituary list of members of the royal family, it is widely accepted to include King Charles and Prince William.
On Astra and IRN1, the bulletin starts at 10:59:00, with the newsreader crossing to Big Ben in London at 10:59:55 for the two minutes' silence and the Last Post.
In addition to scripts and copy written by IRN journalists, access is also available to Press Association news wires, weather forecasts from the Met Office and a breakfast showprep service from Murf Media.
IRN operates two audio channels on the Eutelsat 9B satellite: IRN1 transmits the hourly news bulletins, live sports reports and the classified football results.
Many community, student and hospital radio stations around the UK take the hourly bulletin service.
Copy and audio cuts are also used by BFBS Radio in addition to stations in the Republic of Ireland, Spain, Cyprus, UAE, South Africa and Australia.
The service also includes reports from Six Nations Rugby matches, Wimbledon, England home football and any other major sporting events.