You’re a one-woman party in Westminster with a huge caseload of constituency work and a crucial election coming up, so why write a book as well?

The book is about the anger that I felt seeing up close just how badly Westminster works, frankly.

I think if most people recognise the lack of scrutiny that most legislation gets, they would be shocked.

It would be so easy to bring Parliament technically up to a place where it was working more efficiently. And then you’ve got more of the political challenge of trying to get some of the power away from the whips.

They pack the Bill committees with yes-people who aren’t going to do any scrutiny at all.

All of that, I just felt people should know.

As one of the more radical MPs, how difficult have you found it to remain true to your principles in Parliament?

 Some MPs, who are pretty well fed and watered, come out of the bars and then go to vote on inflicting austerity on some of the poorest people. I’m not alone in finding that somewhat distasteful.

People in there longer than I have been are making similar criticisms and it is possible to work together.

I work closely with back-bench Labour MPs, including Jeremy Corbyn, John McDonnell and Katy Clark, and also have strong links with the SNP and Plaid.

That’s one of the positive things for me about having been in Parliament.

On the one hand, there’s the shock about just how much in need of radical reform the institutions are, really seeing how bad that was. But the good news was that it’s been much more possible than I thought it might be to work across-party with backbenchers to get things done.

It must be odd then, after five years of working closely with Labour colleagues, to then be fighting an election against their party?

It is odd, and it’s an indictment of the electoral system that we have that forces people who agree about quite a lot to have to fight one another.

And obviously there’s quite a big distinction to be made between backbenchers and the Labour front bench, who are the ones most responsible for having targeted Brighton Pavilion on their hit list.

That sense that they really, really want to get rid of that Green voice in Parliament. It’s not the experience I have working with a number

of backbenchers from Labour or the Lib Dems.

There was a “Green moment” in the 1980s but it never led to any seats in Parliament. How confident are you that the current “Green surge” can continue?

We learned a lot from 1989, when we got 15 per cent in the European elections but didn’t win any seats. To say we were unprepared for success in ’89, I think, would be an understatement.

I think we’ve learned a lot from that. We’re much better equipped now. We’ve got a much bigger national infrastructure — it’s still not big — but compared to ’89 it’s much bigger.

When someone takes the step of joining a political party, they’re normally wanting to get involved. They joining for a reason and we’re trying to capture that.

And of course the surge happening just ahead of the election means there’s a very immediate focus we can give them.

We’ve also got Natalie (Bennett) doing visits all across the country. We’re doing an awful lot more to harness that energy than we did in ’89.

If you are successful, how prepared are you for negotiations in the event of a hung Parliament?

We’ve completely ruled out working with the Conservatives. In the event

of a Labour minority government, I think it’s significant that the Greens, SNP and Plaid are talking together about those first few days after the election.

What happened last time was that it took everyone slightly by surprise how that panned out and there were three days of men behind closed doors cooking up a deal.

What we’re trying to do is to make sure that in the event of a Labour minority government, there’s something on the table — not detailed, but a direction of travel of the sort of things, on a case-by-case basis, we would want to put pressure on Labour for in return for votes on certain issues. That degree of preparation is different this time around.

And what will be your “red lines” in negotiations with Ed Miliband?

We’d want to see something serious on climate change and the rolling back of austerity.

One of the most depressing visions of the last few months was to see so many Labour MPs, with some honourable exceptions, marching in the aye lobby, following George Osborne with his Charter for Budget Responsibility — so-called.

It would be lovely to say: “Labour, don’t have an austerity budget.”

Maybe if they’re so dependent on the Green, SNP and Plaid group that can be achieved.

And it’s one of the ironies that under this “greenest ever government,” all of the taxpayer-funded schemes to help people on low incomes to keep themselves warm went.

We want to see greater ambition on ring-fencing funds from carbon taxes and investing those in a massive home insulation programme.

We’ve got the Paris climate talks in December so we’ll be pushing to get some serious commitment from a new government around energy efficiency by then.

Will yourself or Natalie lead those negotiations if they take place?

I would imagine that’s something we will do together. With the TV debates, it clearly has to be one person. And so the broadcasters made very clear it has to be the leader.

There was an earlier suggestion, much earlier, not as the result of the famous interview, that we might do one each. Why wouldn’t you? Different people appeal to different audiences. But they ruled that out.

But for the discussion I would imagine I will be there and Natalie will be there. And then we’ll have to go back to consult the wider party.

You can buy Caroline Lucas’s new book at portobellobooks.com/honourable-friends.