Have you been cheering for the excellent Johanna Konta at Wimbledon? Go, Jo! Or should that be Go, Yo? Johanna (pronounced Yo-harner) was born to Hungarian parents in Sydney and came to Britain when she was 14; her parents moved to Eastbourne while she went to train in Barcelona. She became a British citizen in 2012.

Is she really British, then? Or is she a Plastic Brit, exploiting our great nation for what she can get? Greg Rusedski came from Canada to represent Britain at tennis in 1995, aged 22, even wearing an ill-advised Union Jack bandana. The Lawn Tennis Association (Britain’s national federation) later tried to persuade Novak Djokovic to become British; there were agitated talks during the Davis Cup tie between Britain and Serbia and Montenegro in 2006. I suspect the LTA took one look at his surname and decided he must be Scottish. But he stayed Serbian.

The England cricket team is fresh from victory over South Africa. Who is the more English cricketer: the fair-haired Keaton Jennings with his mother from Sunderland, or Moeen Ali, with his vast Islamic beard and a grandfather from Kashmir? Jennings was born in Johannesburg and played cricket for South Africa under-19s; Ali was born in Birmingham. Before you make your choice, remember that Ali took ten wickets and scored 94 runs in the match.

The captain of the England one-day cricket team is Eoin Morgan, who used to play for Ireland: the Irish are not ecstatic about being England’s feeder-nation. English cricket’s greatest moment this century came in 2005, when Kevin Pietersen’s mad inspiration gave England victory in an Ashes series for the first time in 18 years; Pietersen was born in Pietermaritzburg and came to England aged 20.

Owen Hargreaves played football for England at the 2006 World Cup. He was born in Canada and spent the first half of his professional life in Germany. The Football Association tried to recruit Adnan Januzaj — one of the Herefordshire Januzajs, I think, ho ho — who is a Belgian of Albanian extraction. He chose Belgium. The England rugby union team includes Billy Vunipola, who was born in Sydney and whose father was rugby captain of Tonga. He was educated in England and had a rugby scholarship to Harrow. Maro Itoje is another England rugby player; he was born in Britain to Nigerian parents and also went to Harrow.

Any more? Zharnel Hughes, a promising sprinter sometimes tagged as the next Usain Bolt, was born in Anguilla and declared himself British in 2015… it’s just one more example out of hundreds as athletes across the world change nationality at a bewildering rate, sometimes because there’s a better deal to be had or a better chance of playing international sport, and sometimes because, well, that’s just the way the world is nowadays; restless, volatile, uncertain, with a million opportunities for travel and escape and advancement and adventure. There was a special team for refugee athletes at the Olympic Games in Rio last year: might as well make that a permanent fixture, because we’re not going to run out of team members.

We all want sport to deliver elemental simplicities — come on Tim! But to our constant disappointment, sport takes place in the same world that we inhabit, and the doubts and ambiguities and uncertainties that plague us become dramatised in sporting action. In the 1960s and 1970s tensions between races in Britain were, at least to an extent, eased by the marvellous feats of black footballers. In India last winter, the England cricket team contained four Muslims.

Nationality is becoming slippery, less downright, less obvious. Jacques Rogge, former president of the International Olympic Committee, spoke of changing nationalities in sport: ‘We cannot oppose this is because it is a sovereignty matter, but let me tell you something; I don’t love that.’

In track and field, many athletes have transferred from Africa to Bahrain and Qatar. The International Association of Athletics Federations has temporarily stopped all shifts of allegiance and new rules are due later in the year. The president, Sebastian Coe, said: ‘It is abundantly clear that… the present rules are no longer fit for the purpose.’

It’s a complicated world, full of aeroplanes and people and politics and religions and money and races and nations. The reality of nationality has shifted drastically while ancient ideas of what nationality means live on in pre-articulate forms deep in our collective unconscious. In sport we lunge instinctively towards a simple partisanship: and find the issue more complex with every passing year.

Simon Barnes discusses Britain’s newest national treasure on the Spectator Podcast: