There was nation wide alarm last night when the Greenwich Time Signal pips failed to sound at 5pm. The disconcerting silence made the front page of today's Telegraph. All sorts of conspiracy theories are circulating.

I've been down to the Starship Enterprise-like control room of Broadcasting House to find out what happened. An engineer drew boxes and dotted lines for me and was kind enough not to stray into difficult physics.

It goes like this: there's an atomic clock in the basement which is itself synchronised with the GPS and a signal transmitted from the National Physical Laboratory in Cumbria. In fact there's a pair of these clocks, in case one should fail. They regulate all sorts of delicate technology in the building.

They also emit a signal every 15 minutes which is turned into audio pulses by a separate bit of kit. These pulses can be picked up by continuity studio and broadcast as the pips just before the hour. Shortly before 5pm yesterday there was a failure of the power supply to the box that generates the audio, so although the clock was keeping faithful time, no signal reached the studio and we had that eery silence before the hour. By 7.45 the problem had been solved and the reassuring beeps restored in time for 8 o'clock.

Denis Nowlan is the Network Manager Radio 4

• Read about the history of the pips in the Wikipedia entry on the Greenwich Time Signal.
• Picture caption: "Broadcasting House : 1937 01/06/1937 © BBC Picture shows BBC Broadcasting House in 1937."

We reported briefly at the weekend about the cancellation of Any Questions (and, as a consequence, of Any Answers). Just as the blog was wondering what happens in these situations (is there, for example, a whole alternative universe of programmes in reserve for every eventuality?) Katy Hubbard, Presentation Editor for 4 and 4Extra, popped up on PM with the answers.

Paul Murphy is the acting editor of the Radio 4 blog

• The picture is from the BBC archive and the caption reads: "Picture shows - European Presentation Department, which is responsible for studio and transmission arrangements.Mr J Foreman gives instructions to a studio manager. 1943"
• Transport allowing, Any Questions will be back on Friday at 2000 (and again on Saturday at 1310, followed by Any Answers at 1400).

I like to think that every week on PM is a special week, but for regular listeners, this week will be... shall we say, extra special? For this is the week that the great Alexander Faris, composer of the Upstairs, Downstairs theme, will speak unto the nation.

For new readers: over the last year, PM has had a regular economics and business slot to cover the recession. We asked the listeners to name the segment, they nominated 'Upshares, Downshares'. Admittedly, we started playing the tune. But we never asked the listeners to start sending in their own versions. They just did. I haven't counted how many yet, but here follows a small selection of highlights. We've had: a reggae version, an Ennio Morricone version, a Russ Conway version, a Bee Gees version, a version by Mercury Award nominees, Led Bib, and a retro arcade game style. We've had recorder groups, several accordions, a choir, a barbershop quartet. Listener Kit Morgan has sent seven excellent BBC themed versions, including this radiophonic workshop version:

And last night, on PM, we heard what Sandy Faris has made of it all, and how he's going to spend his royalties:

And later this week - the definitve Upshares. I can't say more. Stay tuned.

Joanna Carr is Editor of PM

• Lots more about Upshares, Downshares on the PM blog.
• PM is on Radio 4 at 1700 Monday-Saturday. Listen again here.

In the hour or so before Prime Minister's Questions today, MPs were invited to another event. In one of the Commons' committee rooms, the National Heritage Memorial Fund announced it was donating half a million pounds to save the collection of Siegfried Sassoon's private diaries and pocket notebooks which were compiled while serving on the Western Front.

The collection also includes an autographed manuscript of 'A Soldier's Declaration' which when it was first read out at Westminster in 1917 caused a national storm. Sassoon claimed that the war was being prolonged by those who had the power to end it. Ninety years on his statement was again read out loud - by the writer and author Michael Morpurgo. Michael kindly came in to read it again for PM.

Tony Pilgrim is head of scheduling and planning at Radio 4 - he's currently working on attachment at PM

• The donation was covered in The Times and The Cambridge News.
• Thanks to the executors of G.T. Sassoon (deceased) for the picture.

For quite some time we've been musing about the weather on Radio 4.

We know it's a very important part of the schedule and I am frequently assailed by listeners who think we don't give it enough attention, are not clear enough or are negligent about their part of the country - and more. Much more.

Last month PM and iPM tried various different ways of doing a weather forecast - and there was a great deal of audience reaction. Peter Gibbs - from the Met Office - was the man at the helm.

From today we are going to try a new way of telling the audience about the weather on PM. The key changes are:

• Forecasters will use a new standard map of UK weather regions, so the naming of region will be consistent.
• Cear signposting of each region before each bit of weather information.
• The forecaster will pick out some major population centres and the narrative will normally flow from South to North (although this will change in the case of major weather disruptions elsewhere).

So - we'd like to know what you think. Respond here or on the PM blog and I will peruse your responses. It's not a vote - and we will have to decide what we think is editorially best - but I will note your applause, abuse, doubts etc. With interest.

• The changes are previewed on the PM blog and you'll be able to hear the first of the new forecasts at 1757 this evening.
• UPDATE: less than an hour after the first of the new bulletins the PM blog has already attracted 87 comments about it.

editor's note: these remarkable pictures, taken by Hugh Sykes in a US 'theatre internment facility' in Iraq, caught my eye on the PM blog. See the rest of the pictures and leave comments on the original post - SB.