Three Conservative councillors in Brighton and Hove have jumped ship this week, to the consternation of their colleagues and the unbridled glee of their opponents.

Defecting is sometimes spoken of as the greatest political crime of all but it isn't really. Two men generally considered to have been the greatest prime ministers of the past 150 years, Gladstone and Churchill, both changed parties.

Indeed Churchill did so twice. They were politicians of great tenacity who had long careers. They were able to survive other crushing political blows and reappear.

There have been others far less fortunate and not a few who disappeared without trace.

Chief among them was Ramsay McDonald, first Labour premier who still has not been forgiven by the faithful for abandoning what they felt to be Socialist principles so he could head the government.

Sir Oswald Mosley, thought bright enough by many to have led either the Conservative or Labour Parties (and he was in both), founded the New Party and took many followers with him.

All but the most blinkered disappeared within a few years as the undoubtedly talented but flawed maverick descended into fascism.

The Gang of Four who left Labour just over 20 years ago to form the SDP found their experimental political aircraft grounded, with only the Democrat name added to the old Liberals as a mark of their presence.

All four now reside in the House of Lords but they could justly claim New Labour was not far from their goals.

Some defectors simply end up as political jokes. One was Woodrow Wyatt, a Labour MP who ended up, like so many others, in the Lords.

A crashing snob, Wyatt was a socialite rather than a socialist and his main redeeming feature was to write an entertaining series of diaries.

Another was Shaun Woodward, the wealthy Tory MP who joined Labour and who was plagued during the last General Election by a man dressed as his butler.

The public doesn't like defectors. I can remember only one MP who tested the political temperature after switching parties. Bruce Douglas-Mann, an ethical Labour MP whom I knew as a councillor, resigned his seat in London on joining the SDP. He lost.

In Brighton and Hove there have been many previous changes of party. One socialist joined the Communists. Another more entertainingly joined the Scottish Nationalists. Two stalwart Tories in Hove startled everyone by joining Labour.

At the time of the SDP, the unfortunate Liberals on Brighton Council were inundated with defectors from both sides, some of whom were seen off with indecent haste by the major parties.

They were lumbered with their additions, it being an unwritten rule you never reject a defector no matter how unwelcome. Council defectors too seldom win their old seats in new guises.

They have to be exceptional to do so. One was Brighton's wartime mayor, Victor Nicholls, who proved bigger in every sense than his party by defeating the Tories in a contest after some local spat with them.

Often the defectors say it would be good if the party politics was taken out of local government. They arrive on a council representing one party and find half the time they agree more with their sworn enemies. The grass looks greener (or redder or bluer) on the other side of the political fence.

But look at local elections and the party labels triumph over the independents nearly every time.

They may want the party to be over but, as the current week's crop of defectors will learn, it isn't yet. Not by a long way.