Within days of becoming US president, Donald Trump has fundamentally changed the political landscape. It’s a revolution and the world has never seen anything like it…

Or has it? Here in Britain we have painfully short memories. In May 2010, despite failing to win a majority by any definition, the Tories seized executive power and announced a bold new programme designed to shrink the state on an unprecedented scale.

At least Trump is only doing what he said he would. Nowhere in the 2010 manifesto did the Tories say they would privatise the NHS, hand over much of our broadcasting to Rupert Murdoch, centralise state power by decimating local authorities, and abandon the principle of fair taxation by shifting tax relief from the poorest to the richest.

The Tories couldn’t have achieved their revolution without the Lib Dem coalition, who failed to see that their involvement in this revolutionary ideological project to create The Miniature State – or, to use its Orwellian title, The Big Society – was sure to alienate their core support.

But now is not the time to be apportioning blame: instead, to be learning from the mistakes that were made across the opposition. It wasn’t clear until Cameron won an actual majority in 2015 that something different was required. Many saw this, and the hundreds of thousands who flocked to join left-leaning parties understood that change had to involve more than putting a cross on a ballot paper every five years.

We are in a dark place now. It would be easy to lose heart, but we have great ideas and people willing to fight for what we believe in.

There are three vital lessons from the events of the last two years. First is a reminder why Margaret Thatcher held power for so long. In the 1980s the Tories and far-right were regularly beaten on popular vote share by the left and centre-left, but our refusal to work with the SDP and Liberals at seat level kept us permanently out of power.

As the cries of betrayal echo again across the Westminster benches, and as Labour and Lib Dems bicker about what kind of Brexit we may still achieve, cross-party alliances seem unlikely. But we all know, deep down, the differences between Labour, the Lib Dems the SNP and Greens are not so important as to keep a left coalition permanently out of power in our first-past-the-post system.

We have to bury our differences, and nowhere more so than within our own party. Slowly, it appears both sides are emerging into the light and, in my limited experience at local level, members are finding it far more productive to talk about the present and future regardless of their preferred choice as leader.

Which leads to the second point: even in this age of “smart bombs” and drone warfare, politicians always talk about “troops on the ground” as the only way to win wars. Well, as right-wing strategist Steve Bannon said when he first met Trump, “this is war”. And we have troops on the ground.

Numbers alone are not enough, we need to engage with people who disagree with us, and make a case for Labour as the only party capable of delivering a fair Brexit, and saving the NHS. Don’t laugh – it’s as crazy to write off Labour now as it was to declare the end of the Lib Dems in May 2015.

And finally, at the risk of alienating almost everyone still belonging to the party, I suggest we learn from Alastair Campbell. Whatever else you think about him, his ability to keep the whole party on message made it harder for our opponents to attack us. We have local meetings, councillors and MPs to hold to account within Labour, we don’t need to argue about it in public, do we? Honestly, what are you gaining by slagging off Blairites or Corbyn on social media? Aren’t there enough Tories doing that anyway?

You’re never going to agree with each other, so why not agree to differ and spend the time saved by emailing your local Labour branch and asking how you can help. You’ll soon work out who the real trolls are. Let’s all stop arguing politics on Twitter and Facebook and start engaging with real people instead.