Apologies to BT: The Speaking Clock is Correct

I'm starting to realise what it's like to be Boris Johnson. This is the second time I've had to publicly apologise in a month.

My previous post, stating that the Speaking Clock was four seconds fast, was not entirely correct. It appears that although the speaking clock messages that I was getting on our telephone system at work have been incorrect, the BT Speaking Clock service is running perfectly.
The most likely culprit for this peculiar problem probably resides somewhere in the telephone system of a third party communications supplier.

Some very helpful comments from one of my long-suffering followers, drew my attention to the fact that our telephone network is no longer a strictly BT operation, so it was quite likely that some third party complication could have nadgered the normally reliable service.
I also had a chat with a chap from The Greenwich Observatory. Although he explained that they are no longer "The Keepers of Time" at Greenwich, his assessment of the problem was in line with Jon's explanation.

Apparently you can effectively buy a speaking clock device for your telephone network. This uses a radio timing signal, broadcast from Anthorn in Cumbria, to keep it locked to the correct time. Unfortunately, if your speaking clock box loses the timing signal, it continues to operate but uses its own internal quartz crystal oscillator to keep on time. If this oscillator isn't running at the right rate, the thing will gradually drift off.

It's plausible that this is what's happened to the rogue speaking clock which I was using.

If it does get sorted out, I'll let you know, but until then,
"At the third stroke, it will be time to make a grovelling apology to BT... PIP...PIP...PIP"