Half a dozen TV channels including Channel 4 and Channel 5 suffered an outage during prime time on Saturday evening because of a technical problem.
Channel 4 and its sister channels, More 4, Film 4 and 4 Music, were down for more than an hour. Channel 5 was briefly affected but the output returned.
A Channel 4 statement said: “We did come off air due to technical issues and steps were taken to put this right as soon as possible.”
Some of the Channel 4 channels appeared unable to play adverts or were showing a holding screen instead of the programmes. Others showed a blank screen with green lines.
The problem was caused by an unplanned evacuation of the west London transmission centre of Red Bee Media, the company that plays out the channels.
BBC continuity announcer Duncan Newmarch, based in the building, tweeted: “I’ve just spent the last two hours stood outside the building. The fire alarm rang out and we could smell smoke in the corridor so had to evacuate – nobody’s hurt.”
He added that BBC One and BBC Two could remain on air as they were being broadcast from Salford.
London fire brigade said it was called to reports of a fire alarm going off but there was no fire.
While BBC channels were generally unaffected, they were unable to air the usual continuity announcements, instead using generic ones before Strictly Come Dancing and its BBC Two coverage of the Chelsea Flower Show.
Channel 4 viewers missed a large chunk of Bettany Hughes’s Treasures of the World, with the channel showing Britain’s Forgotten Wars with Tony Robinson when it returned. More 4 viewers missed the start of Inside Rolls-Royce.
When the feed came back on, some viewers reported briefly seeing BBC idents on the rival channel.
