My father, who was wounded on the Normandy beaches, often repeated Aristotle’s line that true courage was the middle point between cowardice and foolhardiness. He insisted that it came from the ability to face reality.

I came to the same conclusion in a different way. Having followed in my father’s footsteps as a public servant in Indonesia, the Balkans, Iraq, and Afghanistan, my life was changed not through my work but through the two years I spent walking across Asia, staying in over 500 village houses. It was there that I noticed most starkly the grotesque gap between the rhetoric of governments and the reality on the ground.

Of course we must deliver Brexit. But we can’t do it by pretending that Europe is likely to offer a different deal, or that some lethal enigma called “No Deal” could be driven through against the wishes of parliament. We must acknowledge that the Conservatives do not have a majority in parliament, that the wrong Brexit would have a devastating impact on Northern Ireland and Scotland’s place in the union, and that high European tariffs would destroy our agriculture and threaten the jobs of the million people who work in our automotive and aeronautic sectors.

I would bridge the gap between the referendum result and parliament through a citizens’ assembly, a grand jury, which would help the public to focus on the practical details, take the party politics out, and define again for parliament not the “what” of Brexit but the “how”. But I am not pretending parliament is anything other than it is, or that any policy, including mine, is guaranteed to work – merely that this is the best, the fastest, and indeed the only chance of getting Brexit done.

The grand optimism of politicians is too often a cover for deep pessimism Rory Stewart

And I am a Conservative who is prudent about finance. I won’t commit to “turn on the spending taps”, or put £40bn into a single department, or to cut taxes alongside a no-deal Brexit. Such promises risk destroying the Conservative party’s reputation for economic competence. Instead, I would use the money available to invest in education and in the infrastructure, from broadband to rail lines, that will transform productivity – particularly in the north. I would borrow to build 2 million more houses. But I would only borrow against marketable assets like houses – which the government can then rent out or sell. I would invest in research and development in British universities to develop the solar technology of the future. I would introduce a universal National Citizens Service for 16-year-olds focused on community projects. I would work with other parties on a national plan to fund social care. But I would not spend money we do not have.

The grand optimism of politicians is too often a cover for deep pessimism – an uneasiness in the face of a difficult world and a struggle to believe in the practical steps necessary to improve it. But what I discovered as the deputy-governor in Iraq, or setting up a charity in Afghanistan, was the same thing that I learnt as the flooding or prisons minister: the more you acknowledge real problems and real constraints, the more remarkable the change. It doesn’t matter whether you are clearing 30,000 truck-loads of garbage out of the old city of Kabul, or making Britain lead the world in its approach to the environment and the climate cataclysm: what matters is facing reality – and having the determination and energy to force change through.

Rory Stewart is secretary of state for international development