Kenningham thinks Biden could even lean into the age discussion and make light of it. “The way that Ronald Reagan brilliantly quipped ‘I will not make age an issue of this campaign. I am not going to exploit, for political purposes, my opponent’s youth and inexperience.’ He got a huge laugh, and Walter Mondale knew he’d lost.”

There are also little tricks you can employ, reveals Kenningham, “like taking a sip of water if you’re asked a difficult question, which gives you time to reflect, or asking a question back. What seems like a long pause to you isn’t long on TV. You can also say you don’t know something. People like Biden’s honesty.”

There’s a fine line between being prepared and overprepared, says Harri. “If this doesn’t sound contradictory, they’ve almost got to organise spontaneity. We know Biden can be wheeled out to the podium and deliver a script.

“He did that well with the State of the Union address. But there will be an opening when Trump goes rogue, and Biden needs to seize that moment. Then he needs to react: to tut at Trump, come back at him with biting wit, and flag up Trump’s fundamental flaw.

“We need to see a spontaneous mind at work, so that Biden is more than just a figurehead. He could win this debate visually by pulling the right kind of face when Trump says something borderline mad.”

That’s a key point. It’s vital Biden remembers that this is a TV performance too, and that he’s on camera throughout. “You’re sending signals all the time: more than 50 per cent of what you’re communicating is non-verbal,” says Harri. “So when the moderators or Trump speak, it’s critical Biden doesn’t drift off and stare into space.”

Kenningham recalls how George Bush Sr was spotted looking at his watch during a presidential debate in 1992. “That became a defining moment and was immensely damaging. There’s also the handshake at the beginning: who goes in first can confer power. If Biden comes out and takes the initiative, and seems really energised, that will set the tone.”