April 6, 1970 saw the first edition of PM. The presenters - William Hardcastle and Derek Cooper - promised a programme that "sums up the day and your evening starts here."
A new style - and a new sound: the programme was the first radio news programme to have its own signature tune ... unless you include Big Ben at the start of the Six o´clock News.
Some of radio´s biggest names presented PM in its early years. After William Hardcastle came Steve Race, Joan Bakewell, Bob Williams, Susannah Simons and - of course - Valerie Singleton. Pre-interview chats with increasingly youthful junior Ministers inevitably began with a sheepish admission that "I still have my Blue Peter badge".
In the late ‘70s and early ‘80s, one of the best-known, and best-loved, voices was that of Gordon Clough. Gordon, who died in 1996, had an idiosyncratic way of preparing for the programme; he would complete the Times, Guardian and FT crosswords in a matter of minutes before turning to translate another tome of Russian literature, all the while working his way steadily through his daily ration of sixty or so cigarettes.
Smoking is now banned in the PM production office. Another disappeared vice from those years was the mid-programme tipple. It was a production secretary's duty each day to take the presenters their choice of spirit (doubles) and mixer.
As Gordon would remind every new generation of PM producers, he began life on the programme as an editor. He was banned from that role and had to turn to presentation after running out of material one evening, with more than 20 minutes left of the programme. Those producers, incidentally, included some who went on to become senior figures on the BBC - Jenny Abramsky, former Director of Audio and Music, and Tony Hall to name but two.
But Gordon´s lapse was rare. Over the years, PM has become renowned for its ability to make immediate sense of things as major stories unfold: a special on the unmasking of Anthony Blunt; the assassination attempt on Pope John Paul II; the explosion of the space shuttle, Challenger; the first report from inside General Jaruzelski´s Poland; the Church of England's vote for women priests; and the "rose-garden" resignation of John Major. All of these were breaking as PM went to air.
The PM signature tunes have always been a source of controversy. There have been three. The last was dropped when Princess Diana died in 1997 during the period of mourning - and it never came back. No one, except the then controller, seemed to notice.