Sunder Katwala is the Director of British Future.

The resignation of Afzal Amin as Conservative candidate in Dudley North is perhaps the most extraordinary political story that anyone can remember. As cunning plots go, Afzal’s fake EDL protest may have turned out to owe more to Baldrick than Machiavelli, but the candidate was playing with fire, apparently willing to risk stirring community tensions to try to save his faltering campaign.

Given Afzal’s eleven years service in the British Army, it is a shame to see his political career end in disgrace. The Conservatives must surely come down like a ton of bricks on any candidate who treats with the EDL in this way – and so a British Asian candidate should expect nothing different. By the same token, Afzal’s personal catastrophic error of judgment shouldn’t deter the party from giving future ethnic minority candidates a fair shot, any more than local associations should turn down the next ex-soldier to step forward.

Nor should it overshadow the scale of the recent Conservative achievement in breaking Labour’s monopoly on ethnic diversity in Parliament.

When David Cameron took over the leadership of his party, the Conservatives did have two non-white MPs compared to thirteen from Labour. A decade later, that gap has disappeared. For the first time ever, which party is making the greater contribution to the ethnic diversity of the House of Commons will depend on the General Election swingometer.

If the two parties were to win in May the Commons seats that they currently hold, each party would have eighteen non-white MPs.

If David Cameron can emulate John Major’s majority victory of 1992, then the Conservatives will overtake Labour on ethnic representation in Parliament, a historic shock to Labour given its historic record in this area.

Ed Miliband can expect to have more non-white MPs than the Conservatives if Labour is the largest party.

If there is a Conservative-led minority government, the parties are likely to be only one or two MPs apart in the ethnic minority stakes, making it a perfectly reasonable ambition for the Conservatives to seek to overtake Labour by 2020, if not this time around.

So the British Future analysis of diversity in Parliament clearly shows that most of the progress in the last decade has been among the Conservatives. David Cameron deserves credit for his successful political leadership on this issue. Despite inheriting weak foundations, he has in ten years emulated more quickly the scale of progress which it took Labour nearly 25 years to make, from 1987 to 2010, turning the contest to increase Parliamentary diversity into a neck-and-neck race.

It is easy to forget how recently this was simply assumed to be impossible, and that ‘ethnic diversity in one party’ would continue for the foreseeable future. The Nuffield college election studies offer an authoritative account after each General Election. Its 2005 study reflected the widely held orthodoxy, gloomily predicting that ethnic diversity would remain confined to one side of the House. “Given the political reality that electable non-white candidates were most likely to be those fielded in predominantly non-white constituencies, Labour’s monopoly after 1997 of such seats made it unlikely that other parties would make any significant contribution to increasing the number of ethnic minority MPs”, wrote Byron Criddle in his account of Parliamentary candidates.

That prediction has been disproved. The experts felt that the parties would never trust the voters in middle England to be fair to minority candidates. Local associations and the voting public have proved them wrong.

There has been little of the controversy of the A-list this time around. Yet in Havant and in Braintree, in Fareham and in South Ribble, in Wealden and North-East Hampshire, and in the safest Tory seat of all as the Richmond association sought its successor to William Hague, Tory associations have not batted an eyelid as ethnic minority candidates won several of the hardest-fought selection contests.

Progress should not be a cue for complacency. If citizens of any ethnic background were equally likely to make it to the Commons, we would expect around 65 non-white MPs, rather than the 40 to 45 likely to be elected in May.

Even if incomplete, the recent rapid progress in Parliamentary diversity is important. Over the last decade, Britain has come ever closer to being able to say, truthfully, to candidates for Parliament that they do now have fair chances, and do not face higher barriers for selection or election. That could not have been said twenty or even ten years ago.

That could help the House of Commons to better reflect the country that it serves – but it may not the partisan prize some had hoped for. There is little reason to think that the increase in ethnic minority representation offers any magic key to shifting the votes of ethnic minority voters.

This welcome progress has come about because voters – particularly white British voters – are mostly highly unlikely to vote for or against a candidate based on skin colour. Party colours matter much more.

It ought not to come as a surprise to the political parties to discover that ethnic minority voters don’t cast their votes based on the ethnicity of candidates either. Will we see a non-white Prime Minister one day? It is almost certainly a question of when rather than if. The research suggests that Britain can be increasingly confident that whether somebody like Sajid Javid, Chuka Umunna or one of the new 2015 intake makes it to the top will depend on the content of their character, and their politics, not the colour of their skin.