Newspaper headlines: 'Russia accused over Syria war crime'
The papers are again dominated by the after-effects of US President Donald Trump's airstrikes on a Syrian military base.
The Sunday Times says that, following the cancellation of Foreign Secretary Boris Johnson's trip to Moscow, Britain and America will this week accuse Russia of complicity in war crimes in Syria, and demand Russian President Vladimir Putin pull the rug from what it calls Bashar al-Assad's blood-soaked regime.
It says US Secretary of State Rex Tillerson will instead fly to Moscow to confront Russia with evidence it had knowledge of, and sought to cover up, the deadly sarin strike that left more than 80 people dead.
With the headline "So Vladdy ridiculous", the Sunday Mirror says the foreign secretary was shunted off to the sidelines of world affairs by Russia and the US.
But the Sunday Express believes he was instead right to take the diplomatic lead with the G7, arguing that is "what Britain does best".
The paper also backs Mr Trump's actions.
"It took 59 Tomahawk missiles to tell Assad his war crimes will no longer be tolerated," it says.
Writing in the Mail on Sunday, the former British ambassador to the US, Sir Christopher Meyer, welcomes Mr Trump's show of strength but urges him to "keep up the momentum" and find a way to work with the Russians.
The Sunday Mirror, though, has an article by Labour leader Jeremy Corbyn arguing that, while the horrific chemical attack was a war crime that should be investigated by the UN, Mr Trump's response "risks escalating the war."
The Mail on Sunday, meanwhile, asks whether Ivanka Trump "forced her father's change of heart", noting that the president launched the attack little more than 24 hours after his daughter tweeted that she was "heartbroken and outraged" by the images of what she called the atrocious chemical attack.
"Until that point," says the paper, "the White House had been blaming Barack Obama's policy in the region for the Assad atrocity."
The main story for the Observer is an accusation that the election for the leadership of what it calls the super-union, Unite, has been turned into a "proxy war" against Jeremy Corbyn.
Writing in the paper, current Unite leader Len McCluskey accuses a cabal of right-wing Labour MPs and grandees, including deputy leader Tom Watson, of trying to undermine him and his close ally.
The paper believes the move is likely to "open another chapter in the party's civil war".
Research by fitness body UK Active suggests that 150 minutes of moderate dance exercise a week could significantly lower the chances of cancer, strokes and hip fractures for the over-60s - and save the NHS billions of pounds.
Finally, the Sun on Sunday tells the tale of a collector who bought an old Russian tank for £30,000 - and found about £2m worth of gold hidden in its fuel tank.
Nick Mead, from Helmdon in Northamptonshire, tells the paper he did not know what to do.
"You can't exactly take five gold bullion bars down to Cash Converters," he says, "so we called the police".
Officers took the gold but he is relaxed about whether he gets it back, saying: "I will still have my beautiful tank."