If they were 'off tubing' in the UK, one guesses it was at FOM TV HQ at Biggin Hill.
During the ITV F1 days, the last Suzuka hit typhoon, ITV had three layers of back-up for the commentary, incase it was lost.
If the main Murray and Martin commentary feed - sent down off the main satellite feed was lost, they had an ISDN back up. If that was lost, it was onto the telephone line - and if that was lost, there were two freelance motorsport commentators sitting in a booth at ITV/LWT ready to call the race.
My user name might look like Hatton Cross, but it's pronounced Throatwobbler Mangrove.
UKnews, bkman1990 and Brekkie gave kudos