The decision reached by Nigel Hastilow to resign has spared David Cameron from having to make a deeply unappetising choice.

If he had sacked him, there would have been a backlash from some elements of the Tory grassroots. If, on the other hand, Mr Cameron had overlooked the matter at least one modernising Tory MP was ready to condemn him.

Some activists will still regard Mr Hastilow as a martyr - he claims to have received hundreds of messages of support - but his resignation has taken most of the sting out of the furore.

He quit, he writes in a local newspaper today, because he could not bring himself to sign off quotes written for him by the party’s chief spin doctor, Andy Coulson.

He was supposed to say: “Although I did not and do not support Enoch Powell’s ’Rivers of Blood’ comments, I accept that some of the wording of my column was incredibly stupid.”

One can imagine Mr Hastilow - a former newspaper editor - might object to having to read such a humiliating script but it is difficult to disagree with its thrust.

Mr Cameron was praised on Friday by Trevor Phillips, chairman of the Equality and Human Rights Commission, for the care he had shown in tackling immigration in a speech last week.

The Tory leader had, said Mr Phillips, succeeded for the first time in his adult life in leading a debate on the issue without reference to race.

And then comes Mr Hastilow. Defending himself, he points out that he had said that Mr Powell was right that immigration would dramatically change the nature of Britain. The claim is hardly controversial - the invocation of the speaker and the speech could hardly be more so.

Mr Cameron, an architect of the 2005 election campaign which majored on immigration, saw how the issue can drown out all other messages.

Determined not to repeat what he regarded as one of Michael Howard’s main mistakes, he hardly touched the issue for the first 18 months of his leadership.

It was his public announcement that immigration is “too high” and needs to be “substantially” cut that helped re-connect him with the grassroots after the rift over grammar schools.

But the Tory leader has been disciplined in never going beyond that formulation and has been responsible in his language.

All three main political parties are struggling to address voters’ concerns over the issue of immigration without losing destructive forces.

The brief, inglorious career of Mr Hastilow is a reminder of where the line lies through this minefield.

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