The former prime minister was booed by crowds of bereaved families after his first day of testimony on Wednesday as he hurriedly left the building in central London.
Mr Johnson has attended the inquiry appropriately dressed in a suit and wearing a coat to ward off the frosty winter temperatures. But one piece of clothing stood out in particular - his Grimsby Town FC bobble hat.
The comfy adornment no doubt keeps the former Tory MP’s head warm and helps drown out some of the heckling he receives from protesters, but Mr Johnson has not clear link to the football club or town.
Mr Johnson was born in New York and spent some of his childhood near Oxford in the UK, before living most of the rest of his life in London.
He has owned the hat for years after being spotted wearing it while out jogging, at Downing Street and on holiday in the Scottish Highlands.
Mr Johnson has prefviously commented that he likes football, but has never committed to one specific team and hasn’t been spotted at Grimsby Town’s stadium, Blundell Park, to watch a game.
He was asked by Grimsby Live in 2022 why he had such an affinity for the bobble hat. He responded: “It’s what I grab when I run out the house. There’s no particular science to it.”
He added: “It’s a very good hat. It’s lovely and warm. What I like most is that it comes down and covers my ears.”
Mr Johnson did joke with the local newspaper when would it would be “strategically advantageous” to wear the £11 hat to boost Grimsby Town FC’s fortunes in League Two.
So, the former prime minister’s loyalty to his Grimsby Town FC bobbly hat will continue to remain a mystery.
Mr Johnson suffered a torrid time at the Covid inquiry on Wednesday as he stumbled over his words as he tried to explain how he lost 5,000 WhatsApp messages between January 2020 and June 2020.
He also said that the crisis “bewildered” him and that government’s policy at times appeared “incoherent”.
Mr Johnson also defended his under-fire former health secretary Matt Hancock, saying he did a good job in difficult circumstances.
He said he had considered moving the then-health secretary as he came under fire in 2020 but instead backed him, partly because there was no guarantee he would be “trading up” with a replacement minister.