Sir Michael Fallon's resignation is the main story on the front pages of Thursday's newspapers.
The Times says Sir Michael appeared to have weathered an apology issued earlier this week for repeatedly putting his hand on the knee of the journalist, Julia Hartley-Brewer, during a dinner in 2002.
But - according to the Daily Telegraph - friends of Sir Michael said that while no new allegations had been made against him, there were concerns that other incidents which he had previously considered to be "flirtation" were about to become public.
The Sun says it understands Sir Michael had spent the past 48 hours contemplating his past behaviour.
The newspaper quotes a source as saying that Sir Michael had told the prime minister he could not guarantee there would not be more stories like the one involving Ms Hartley-Brewer.
The Daily Mail reports on one source claiming Chief Whip Gavin Williamson had advised Theresa May to fire the minister, although others insisted Sir Michael had resigned of his own accord following a face-to-face showdown in Number 10.
The Spectator says the resignation is a clear indication that the government is keen to show that it takes a hard line approach when dealing with allegations of inappropriate behaviour from those in positions of power.
'The mood in the tearoom'
According to the Daily Mirror, the fear in Downing Street is that Sir Michael will not be the only scalp of the Westminster sleaze scandal.
The Times quotes one minister as saying: "This feels a lot like MPs' expenses scandal. The mood in the tearoom is awful, the worst it's been since then."
The Guardian reports that Mrs May is expected to appoint a new defence secretary without embarking on a wider reshuffle.
According to the Daily Mail, Immigration Minister Brandon Lewis and Security Minister Ben Wallace are tipped as possible replacements.
The Telegraph suggests Penny Mordaunt could become Britain's first female defence secretary as she is a former minister in the department and seen as reliable and a competent media performer.
But the Times speculates about a move for Boris Johnson from the Foreign Office.
The Telegraph says it can disclose that Buckingham Palace is understood to be "not happy" after Labour MPs tried to involve the Queen in a row about Brexit.
On Wednesday, the party used an ancient parliamentary procedure known as the "humble address" to try to force the government to release secret documents about the economic impact of Brexit.
The newspaper explains that, by convention, the Queen must respond to humble addresses, prompting concern that she will, in effect, have to pass comment on a political issue.
Many City analysts are expecting the Bank of England to raise interest rates on Thursday - but the Financial Times believes that, on balance, it would be an unnecessary move and jumping the gun.
It says underlying inflation has been so weak that there cannot be much risk in waiting to see some signs that it is picking up before increasing rates.
The newspaper says that if the bank does put up rates, it should make clear that this is not the first of a series of increases.
Five finger discount
The Sun reports that middle-class shoplifters are on the rise - stealing luxury items such as cheese, wine and Swiss chocolate.
It says supermarket bosses have reported an increase in affluent, middle-aged shoppers who "get a kick out of not paying for a bottle of wine of their Friday night steak".
One manager tells the newspaper: "We are not talking about a few people stealing to feed themselves - they will clear whole shelves, go behind checkouts and take spirits, coffee, detergents, wine, chocolate."