Amid mounting pressure from his colleagues, Hancock wrote a letter to Prime Minister Boris Johnson, stating that the government owes it to people “who have sacrificed so much in this pandemic to be honest when we have let them down,” BBC reported.

In a video posted on Twitter, Hancock said: “I understand the enormous sacrifices that everybody in this country has made, that you have made, and those of us who make these rules have got to stick by them and that’s why I have got to resign.”

He added: “I’m very proud of what we’ve done to protect the NHS at the peak, to deliver that vaccine rollout—one of the fastest in the world—and I look forward to supporting the government and the Prime Minister from the backbenches.”

Johnson said he was “sorry” to see Hancock leave his position, BBC reported.

“You should leave office very proud of what you have achieved — not just in tackling the pandemic, but even before Covid-19 struck us,” Johnson wrote in a letter in response. “I am grateful for your support and believe that your contribution to public service is far from over.”

The relationship between the prime minister and the health secretary was not always as civil, however. A few weeks ago, former chief advisor Dominic Cummings tweeted a conversation between himself and Johnson at the beginning of the pandemic, in which the prime minister called Hancock “Totally f***ing hopeless.”

As reported by The New York Times, Cummings himself was ousted from office a year ago after going to visit his parents despite the lockdown. Since then, he has outwardly expressed his disdain for the handling of the pandemic in Hancock’s hands.

Hancock saw the U.K. through the COVID-19 pandemic, stressing to the public in the last year how important it was to abide by lockdowns and social-distancing procedures.

The Sun, a British tabloid, was responsible for the release of the photos of Hancock kissing his recruited advisor Gina Coladangelo, and reported that the photos were from May 6.

Hancock, who is married with three children, expressed in his resignation: “I want to reiterate my apology for breaking the guidance, and apologize to my family and loved ones for putting them through this. I also need to be with my children at this time.”

Newsweek reached out to Johnson’s office for further comment, but has yet to receive a response.

Updated 3:06 PM ET, with additional information.