Dear John, I really hope you won’t be offended by this letter from your uncle. I have nothing but respect for you and I would hate to damage the friendly relationship we have had since I first met you when you were six years old.

I understand from your aunt that you voted Labour in the latest election and that you are a ‘Corbynista’. In fact even your aunt herself — a lifelong Tory as far as I know — has been saying how nice Jeremy Corbyn is and how much better he handled the Grenfell Tower tragedy than Theresa May did.

Of course, you can vote for whoever you like and it’s none of my business. But I take the risk of irritating you because I would like to tell you why I did not vote for Corbyn.

I suppose this is going to sound like ancient history, but I became politicised in the early 1980s. I got a job in Hong Kong: then a relatively poor, ramshackle little remnant of the British Empire. Still, thousands of penniless refugees were risking their lives by crossing from mainland communist China to get there. I stayed some nights in a shanty town with no proper sanitation and the stink of human excrement.

Hong Kong was an unusual place in lots of ways but its economic policies were truly extraordinary compared to most other countries’. The highest rate of income tax was 15 per cent and there was no capital gains tax at all. Because of various accidents of history, the government’s role was minimal. Hong Kong offered free trade relations with every-body. It had zero tariffs on imports. It was  the nearest thing to a purely capitalist territory in the world. The result? An economy that grew like a triffid. Growth at 6 per cent a year was normal. Anybody could start a business and have a chance of success. The place buzzed with entrepreneurial spirit.

I met an economist there who told me that at this rate of growth, the GDP per capita of Hong Kong would overtake Britain’s by 1990. That sounded absurd. Britain had centuries of economic development behind it. Hong Kong was just a barren rock with a large minority of recent refugees. But such was the fabulous rate of growth generated by capitalism that my friend proved to be correct. By 1990, it did indeed become wealthier per capita than Britain.

After leaving Hong Kong, I had a short stint in Tokyo and then returned to Britain by train, travelling through China, the Soviet Union and Romania. All these countries were communist and the signs of economic stagnation and failure were obvious. In China, I saw a farmer pulling his cart by hand. He couldn’t even afford a horse. I stopped in Irkutsk, Siberia for a night or two. I was beginning to long for fresh fruit, so I walked around the town looking for some. After a lengthy search, I could only find two hard, stale little lemons. The Soviet Union was so poor I was advised to take packets of Kent cigarettes because these were a kind of unofficial currency. I did, and saw that they were treated like gold nuggets.

In Romania, the lighting at night was always set very low because the country could not afford the electricity, I discovered a supermarket with a long chilled food cabinet. It was not chilled and was empty except for a few tins.

You may be thinking, ‘Well that’s all very well but what has it got to do with Jeremy Corbyn and the modern Labour party?’

Jeremy Corbyn and his effective deputy John McDonnell are self-declared socialists. They believe that the state should control the ‘commanding heights’ of the economy — the big industries. The dividing line between socialism and communism has never been very clear. Most of the regimes we refer to as communist actually called themselves socialist. (The full name of the  Soviet Union was the Union of Soviet Socialist Republics.) Karl Marx viewed socialism as a stepping stone to the more perfect world of communism.

McDonnell has waved Mao’s Little Red Book in the House of Commons and says that we have things to learn from Marx’s Das Kapital. He has been filmed talking about insurrection. Marxists do not believe in parliamentary democracy as anything but a temporary expedient on the way to the so-called ‘dictatorship of the proletariat’. I don’t know whether McDonnell has that at the back of his mind as his ultimate wish.

But in any case, we do know this: every single truly socialist country has been an economic failure. Its people have become poorer that those in capitalist countries. The aim of socialism has been to improve the lot of the poor but the result has always been that the poor have done worse than they would have done under a capitalist economy. To care about the poor is to care about the preservation of capitalism.

We have the advantage of two natural experiments: Germany and Korea were both divided into a socialist and a capitalist half. As time went by, the differences in the economic conditions of the poor in both countries became stark. On the socialist side of Korea there has been mass starvation. (The same happened, incidentally, in the Soviet Union and China.) On the socialist side of Germany, the average wage was lower than unemployment benefit on the capitalist side.

I believe 20th-century history provides a graphic demonstration that socialism is an economic disaster. And after the world’s two most populous countries — China and India — permitted more capitalism in their countries, their economic performance suddenly surged. This is the main reason why the past 30 years have seen the biggest reduction in extreme deprivation that the world has ever seen.

There’s one other thing. In every single country that has become socialist and aspired to communism, political oppression has taken place. People have been killed and imprisoned without trial. In some countries including the Soviet Union, China and Cambodia, millions died in what you might call the Communist Holocaust. But political oppression has taken place in every single one, including Cuba and Yugoslavia.

I worry that my children — your -cousins — and others of your generation were not alive during these terrible events and so, quite naturally, are not fully aware of what happened. Because of where I have lived, I am probably more aware of them than most. This, John, is my best shot at explaining why I will never vote for Corbyn. Hoping we are still friends. Uncle James.