This country is obsessed by football. Many of the people who voted to “leave Europe” follow closely the ups and downs of the teams in the Premier League, teams whose stars and managers are often from, well, “Europe”.

It is unimaginable that any football fan would want his or her team to descend from the Premier League to the lowest, just like that. Yet that is not unlike what this country would be doing if the wishes of the Brexit extremists were to be realised.

The analogy was made recently by a man who ought to know, namely the distinguished French civil servant Pascal Lamy. Lamy is a former director of the World Trade Organisation, into whose rulebook hard Brexiters wish to precipitate us if a stop is not put to Brexit.

At a recent event at the London School of Economics in honour of the late Peter Sutherland – the man who set up the WTO and whom Lamy succeeded – the latter could hardly have put it more plainly: “The internal market is the top league. The WTO is the bottom.”

The internal market is usually referred to in the UK as the single market, of which Mrs Thatcher was a passionate supporter, arguing that it would give the UK economy “access to over 300 million of the world’s most prosperous people, bigger than Japan, bigger than the US. It’s not some bureaucrat’s dream – it’s for real.”

The propagation and membership of the internal/single market was considered by former Tory chancellor Kenneth Clarke to be Margaret Thatcher’s greatest achievement.

The idea of trying to set up new trade agreements in a world that is going protectionist fast is for the birds

But, thanks to the trade agreements the EU has with a fair proportion of the rest of the world, as the Office for Budget Responsibility reminds us in its Discussion Paper No 3, “when added to the 49% share of UK trade accounted for by members of the EU, altogether [existing] trade agreements reduce or eliminate tariffs for around 66% of UK trade.”

The idea of crashing out of the EU and trying to set up new trade agreements from scratch in a world that is going protectionist fast is, or ought to be, for the birds.

Now, most media comment about recent OBR pronouncements has concerned speculation about the “wiggle room” that might or might not be available to Philip Hammond in his budget next week. For me the OBR’s observations about the impact of even the mere prospect of Brexit are the real fascination.

The idea that Hammond has “room for manoeuvre” with a budget in the midst of the post-referendum chaos should be seen in the context of a timely report by the Nuffield Foundation and the National Institute of Economic and Social Research. Within the off-putting carapace of its title – Understanding and Confronting Uncertainty: Revisions to UK Government Expenditure Plans – the authors spell out how public spending plans are subject to continual adjustment as economic growth usually turns out to be less than indicated by the ambitious forecasts on which spending plans are based.

The OBR reminds us that, since the referendum, “the UK moved from being close to the top of the G7 GDP growth range in early 2016 to close to the bottom in 2018”.

It goes on: “Business investment appears to have been depressed by uncertainty … while the prospect of weakened access to foreign markets has pushed the exchange rate lower, raising inflation.” The traditional boost to the economy from a devaluation has been thwarted by the internationalisation of supply chains, “which means that many UK exports have a high import content”, but also (and I suspect principally) by “the uncertainty for exporters created by the referendum result (which may have inhibited investment in new capacity), and resilient demand for imports”.

What this economy needs is a statesmanlike – or stateswomanlike – decision to admit that continued membership of the EU is in our best interests, and an admission that we are living in cloud cuckoo land if we do not accept the argument of the veteran economist Robert Neild – referred to recently in this column – that better public services require higher taxes.

In his Quinlan lecture at the Foreign Office last week, Sir John Major described the prospect of Brexit as “a colossal misjudgment”. He went on to say that once the damage became clear, “I believe those who promised what will never be delivered will have much to answer for. They persuaded a deceived population to be weaker and poorer. That will never be forgotten – nor forgiven.”

But it is not too late. Do we really want to abdicate, to mix a sporting metaphor, from our pole position in the Premier League?