Britain's top civil servant has admitted that he must "bear his share of responsibility" as he finally broke his silence over the Partygate scandal.
Cabinet Secretary Simon Case, speaking publicly about the affair for the first time, said lockdown rule-breaking in Downing Street was "horrifying".
In testimony marked by sighs and long silences, Mr Case told MPs that disciplinary action over the scandal was "in train".
He admitted that he could be under investigation too as "nobody should be excluded from disciplinary process" due to seniority.
But in a sometimes tetchy appearance in front of the Public Administration and Constitutional Affairs committee, Mr Case refused to say whether he had spoken to Boris Johnson about trying to get his wife a job.
The Mirror revealed last week that the Prime Minister had discussed with him the prospect of a plum role for Carrie Johnson with the royals.
Despite then admitting he had an informal chat on her behalf, he told the committee he would not comment on "private conversations".
However, Mr Case was contrite over the scale of rule-breaking in Government at the height of lockdown.
"Mistakes were made, boundaries weren't observed, some of the conduct described in Sue Gray's report would be horrifying in any situation," he told MPs.
"People have let themselves down, people have apologised, it's very difficult."
He claimed to have been shocked by the Partygate affair as some gatherings "weren't ever brought to my attention" by his team.
"That's one of the things I find most difficult and am most determined to address," he added.
"Some of these unbelievably difficult things in this report we didn't know, and if we did know we would've acted on them of course. "
But MPs on the committee were incredulous that "clinking bottle and suitcases" escaped the senior civil servant's notice.
Pressed over his own role in the scandal, he added: "All of us in senior leadership at the time must bear our share of responsibility.
"The biggest responsibility we have is to make sure this never happens again, that this sort of behaviour is never seen at the heart of Government again".
The top civil servant was at the No 10 birthday party for which the PM received a fine but escaped police sanction.
He claimed to be unaware of any work done by the Cabinet office which concluded that if he resigned, Mr Johnson might have to as well.
Mr Case said "a number" of people had quit over the scandal, believed to be a reference to five senior aides standing down in one day in February.
He claimed that no officials caught up in the row had been promoted to posts in other departments.
"If people are found under disciplinary processes to have fallen under the standards expected then it wouldn't be right for them to be promoted," he added.
