Ed says: “I’m the Prime Minister! No, I am. Look, really, really I am. I really am the Prime Minister. David gave me a card that says it and everything. Look, it says Prime Minister. In big letters. Next to the bit where it says Tough Enough. Oh, come on. It’s real... Let me into Number 10, please! Nooo, it’s not a fake ID. David said it was real! That’s my face, look. My face. See. No, not the Wrong Trousers. Yes! No. No one’s been hitting me. My nose has changed a bit, yes. Not to make me look tough, it was an operation for, um, apnoea. You know, to stop snoring. Yes, just like the electorate, harhar. Look, I had a deviated septum! No, I never took any Colombian marching powder whatever that is, but I will admit to being partial to Sherbet dib-dabs. Um… Justine buys them. I guess we spend £70 or £80 on them a week, maybe more… Look, officer, the real issue is are you going to let me into Number 10 or… Oh. Well, I’ll wait out here then.”

The Eds must have been smug-ugly about that manifesto front page. Fiscal responsibility for all! Fiscal responsibility pouring from the coffers, like a golden rain of prudence! Their manifesto very carefully sets out all the things Labour promises they won’t do, so they can be big, responsible and loathable like the Tories. But it doesn’t say what they’d do in the likely eventuality that the economy hits the rails again, the same thing that the IMF criticised the Tories for.

I’m feeding that manifesto into a simulation of the UK economy and political scene, Democracy 3. (Read here for caveats about the simulation we’re using). At first, I implement it slowly, limited by the game’s points-based mechanics. It’s a constant struggle to find the cash to implement any policy changes, and there are several manifesto commitments that seem to be unfunded. I implement them by interpreting the new mansion tax to be more stringent and treating the reverse to the cut top rate of tax as a priority, so we frontload our income. With a bit of careful tweaking we’ve got balanced books, and a nice lump of surplus that is, yes, reducing the deficit and paying off the national debt. Balls, I think you’re a genius.

That said, it all goes out of the window nine months into my first term, when the world economy stumbles. Then it stops stumbling, finds the edge and just bungee jumps. I stick to the manifesto commitments and keep implementing expensive new policies for the next year, all the time watching aghast as it plummets and plummets. I don’t know what the underlying game engine is doing here, so I don’t know if this is guaranteed to happen with every party I load up from this starting seed. But it’s going to spell certain doom for the Labour party’s new government if I don’t get our budget in order – already the ratings agencies are talking about downgrading us to BBB because of my hesitancy.

However, the Labour manifesto pledges have ringfenced everything. Education is ringfenced, with no cuts allowed. Healthcare has both been increased and ringfenced, and that’s half the budget by itself. I can’t bring myself to look at welfare – I tell myself that a Labour government wouldn’t kick a department when it’s down. The easiest, biggest thing to cut is the military. That’s a route to utter disaster, I well know. If you don’t want as many assassination attempts as General De Gaulle or Castro, then you don’t screw with the military.

But I have no choice. So heavy military cuts sink in again. Angry squaddies roaming the streets put me on edge, as Democracy 1 & 2 were rather prone to punishing controversial PMs with assassination squads. Still our economy isn’t performing. If I was to be a good Keynesian, I’d run a deficit here, but our pledges have removed that option. I go back to welfare and slash pensions, but it’s not enough.

Can I raise taxes? Who on? We’ve committed to keeping corporation tax low, and we’ve already bled the rich dry with the mansion tax. We’ve also committed to not increasing income tax, VAT or National Insurance… and the Bank of England has control over the money supply, so that’s out. I mean, we’ve really made a virtue of removing all our tools here. I feel like weeping at the situation I’ve been put in.

I realise that there is one other thing I can do. I reshuffle the cabinet to get more big beasts in, irrespective of their loyalty and background. I just want people with influence, because that’ll let us implement more policies.

But what policies? More supporters in football clubrooms? Frankly, at this stage, without any fiscal tools, I’m just going to try to fulfil as many of the party’s smaller policies as possible, and get a surplus on that budget. I look over the manifesto again, and am surprised to notice a loophole. The pledge is only to not raise income tax on the basic and higher rates of tax – but not the top rate that hits those earning £150,000+. I set up a punitive wealth tax and a luxury tax, to hit these guys, that’ll play nicely to the same core vote. And I put rent controls up, to help the poorest.

Ugh. Our credit rating gets further downgraded in the next quarter because of this huge deficit, which pushes up the interest we’re paying on our £919bn national debt hole. The deficit has hit just over £53bn, so our debt’s rushing up. Even cancelling the whole health service (£49bn here) wouldn’t help with that. The global economy is still in the doldrums. We’ve got vigilante mobs in the streets as the crime rate’s so bad. And I’ve done everything Labour said they would in the manifesto. Honestly, I’m at a loss.

So I start extemporising, creating new policies that fit with Labour’s commitments, without being strictly speaking in the manifesto. I issue food stamps to the tune of £5bn, because I want to help the poor. I also loosen the borders, to get some productive immigrants in, then remember I can’t do that because of pre-manifesto commitments and reverse it. And I push more money into the police force and community police force.

A minister threatens to resign over my treatment of capitalists, so I fire him. I start getting worrying security reports about a terror group set up by wealthy industrialists called the Battenberg Group. Then my Lord Chancellor starts kicking up a fuss, so I let her go. And another minister bails the next quarter. I replace them with even more influential members, but the cabinet is extremely inexperienced now.

A few dilemmas pop up – these are Democracy’s methods that force you to act on particular issues. I completely legalise GM foods, because Labour has, allow fracking, because Labour’s happy with that too, and don’t sign up to global climate change protocols like we promised, because the economy’s too weak – maybe later. I also notice that one of the biggest social and productivity problems is alcoholism, so put a few billions towards stamping on that.

While I’m doing this I notice that the global economy looks like it’s bottoming out. Please, please, recover before the election. I keep fiddling. I chuck billions into science funding in the hope that it supports the economy. Our government introduces stronger consumer rights and strong positive discrimination legislation. As I watch, the deficit closes, and reverses. The national debt is much higher than it was when we took office, but we’re paying it off fast now. 49 per cent of the electorate say that they’ll vote for us!

A big problem does start developing just before the election – our taxes on the rich have hit such a degree that they’re fleeing the country and taking their businesses with them, knocking a fifth off our GDP. The recovery means we can plough on, but I’ll need to deal with that in my next, now-inevitable term.

You can see from this chart the story of our first term. The global recession really hit us hard, but our stimulus package kept the country going until the global economy was back on track. Admittedly, we’ve added something like £300bn to the national debt, but I don’t see how I could have done otherwise given the constraints we were under.

Our next term flies by. It feels like we won all the fights we needed to in our first term, and now we just need to see how long we can hold on for, channelling the spirit of Philip Gould. There are a few huge problems to fix – an asthma epidemic, organised crime, homelessness, ghettos, an unproductive economy and the fact we’re a technology backwater.

I push clean energy and stomp on motorists, to deal with the asthma epidemic – but not so hard that I hit GDP again. I subsidise the purchase of hybrid cars, to encourage people to transition, and offer tax incentives for companies that support telecommuting. These are all small, cheap policies that have big effects – indeed, asthma disappears – but then reappears later on, as the hybrid car initiative actually gets more cars onto the roads.

That Brain Drain is a worry, but it’s caused mainly by the Mansion tax. I cancel the other taxes that are affecting it - the Luxury goods taxes and the punitive tax on being wealthy, but have to accept that this is a difficult one to deal with. GDP or equality? Always hard. I cancel the mansion tax, reluctantly, and the problem vanishes.

Despite dealing with the alcoholism epidemic in my first term, Britain is still a country of piss-artists, which is killing productivity. Looking at the charts, I can see the sources are unemployment, poverty and our weak GDP. I make work compulsory for the unemployed – not very socialist, but it’s mainly a temporary measure to get the long-term unemployed used to work. I tell myself that and promptly forget about it.

Gradual tinkering with GDP gets our credit rating back up to AA-rated. There’s a market meltdown, caused by the oversea mortgage market, which knocks the global economy back into the doldrums, but we’re running a surplus of £70bn so we should be able to muscle through it.

And another epidemic kicks in, just before the next election. I’ve made everyone too happy and they’re getting fat – we officially have an obesity epidemic. I bring back in free school meals to counteract it, cancel farm subsidies completely (to raise the price of food without taxing it) and introduce subsidies on health foods. I try a junk food tax, but it hits the poor disproportionately, so scrap it immediately.

And another! Water shortages have started, caused by slowly-rising average temperatures year-on-year. I have to sink a huge amount of money – over £50bn – into a new climate change adaption fund to cope with it. Thankfully, through prudent fiscal management, I’ve actually just managed to pay off the national debt at this point, so we can afford this easily.

With the National Debt paid off, everything becomes easy. Huge budget surpluses mean that we can fund any innovative policy safely so Britain's push in nanotech, robots and flying cars is the envy of the world. Simultaneously, the prohibitive taxes on the richest have eliminated them from the country and political discourse, making the country fantastically equal, productive and prosperous.

Barring a total global meltdown, the country is safe, so there's really little point continuing this. In this purely fantasy world, the Labour manifesto results in Utopia. That's an achievement for the Eds, even if they don't get elected.

Read our methodology here. Follow the rest of the series as it unfolds here. And here's what happened with the manifestos in the 2010 election.