For the first time this week, Liz Truss had to think on her feet.

When she made her victory speech after the result of the leadership contest, she was able to read from a script.

That was also the case when she arrived in Downing Street.

But PMQs was a very different test.

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As she arrived in the chamber, there was a cheer from her colleagues, and lots of congratulations and handshakes for the new cabinet ministers as they arrived behind the Speaker’s chair.

Her new Home Secretary Suella Braverman was beaming, while Chancellor Kwasi Kwarteng joked with colleagues.

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And the mood during her main exchanges with the Labour leader was different to the tone we have become accustomed to at PMQs of late.

The anger and disdain that so often defined clashes between Boris Johnson and Sir Keir Starmer disappeared.

Ahead of the session, allies of the Labour leader told me he was aware he must move away from the “lawyerly” debating style he used with Mr Johnson.

They were aware of the danger of being accused of “mansplaining” – as happened to Rishi Sunak during the Tory leadership debates.

That may explain why, after months of parliamentary jousts about standards and fitness for office, Ms Truss and Sir Keir parried each other on policy.

‘Stark contrast’

Sir Keir seemed to be attempting to tie his new opponent to the record of previous Conservative governments – she has, after all, been a cabinet minister for all three of her predecessors.

SNP Westminster leader Ian Blackford talked of a “Truss tax” when describing her proposed reliance on borrowing – a line he will no doubt use repeatedly in the debates ahead.

When it came to questions from her own backbenchers, Ms Truss’s advisers will have known commentators would be on the lookout for any signs of tension.

Little surprise then that they reacted with delight at Theresa May’s question about all three female PMs being Conservatives.

The jovial tone from Mrs May was a stark contrast to the sharp questions the former PM shot at Mr Johnson during his time at the top.

What became very clear in this PMQS was that rising energy bills will be the issue of the autumn and a new dividing line has been drawn – how to pay for it.

Does the government borrow, with taxpayers eventually footing the bill, or do we tax oil and gas giants?

Sir Keir made it clear he preferred the latter.

The new prime minister had a few good one-liners, which her high-energy hype men and women on the Tory benches lapped up.

It will, however, take weeks for the tone of this new head-to-head to settle.

The two leaders will get another chance to test each other on Thursday when the PM announces her long-awaited (and much-needed) package on energy bills.

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