He is the fictitious journalist from Belgium who may have inspired an aspiring Brussels correspondent from Britain. It seems fitting, then, that it was Tintin to whom Boris Johnson turned once again as his condition began to improve in intensive care last week.

The Telegraph understands that Mr Johnson began re-reading tales of the boy journalist from Belgium that he first read as a child, as he became well enough to sit up in bed on Wednesday.

The books were sent to St Thomas' hospital by the Prime Minister's family. Mr Johnson was the Telegraph's Brussels correspondent in the Nineties, and last year a copy of The Blue Lotus, an early Tintin adventure, in its original French, was pictured in his car during the Tory leadership campaign.

The fact that Mr Johnson was able to sit up and read was the news that those closest to him, including his pregnant fiancee Carrie Symonds, desperately needed.

The Prime Minister first developed coronavirus symptoms - a high temperature and cough - 17 days ago, when he began a spell of self-isolation. The following day, the 55-year-old, who tested positive for the virus, posted a video in which he said he was "working from home" and continuing to lead the "national fight-back" against Covid-19.

Later that day he drafted a letter to every household, urging the country to abide by the lockdown rules and stating, in a phrase that somewhat eerily foreshadowed his own condition: "We know things will get worse before they get better."