By James Landale
BBC deputy political editor
If you have never heard of a fellow called Charlie Whelan, let me introduce him to you.
He is the sort of man who wears tweeds in London. He likes a pint or two. He "tweets". He is happiest at his home in the Highlands.
Mr Whelan was Gordon Brown's spokesman in the 1990s
The brown trout season has just begun and, if there were any justice, he would be spending a few happy hours with rod in hand on the banks of the Spey.
But Mr Whelan is also political director of Britain's largest union, Unite, which bankrolls the Labour Party, whose members are behind the British Airways strike, and which is at the heart of Labour's re-election campaign.
To the Conservatives and some Labour modernisers, Mr Whelan is a dastardly svengali who is mobilising thousands of Unite members to campaign on behalf of Labour.
They see his influence everywhere, not least in the selection of 59 Unite members as new Labour candidates.
They remember his time as Gordon Brown's spokesman, where he was robust with anyone who failed to paint the then chancellor in anything but the finest light.
The Sun newspaper today describes him as "Gordon Brown's favourite attack dog - a foul mouthed Rottweiler with a roguish grin".
To his defenders, Mr Whelan is a fall guy, a bogeyman got up by the Tories to attack Labour in the run up to the general election, a man whose influence is exaggerated so the opposition can claim to voters that Labour are once again in hock to the unions.
So what are the facts? Well, Unite is a hugely powerful political force. It is Labour's largest donor, providing £11m since 2007. Without Unite, Labour would probably have gone bankrupt.
There are 111 members of the Unite group of Labour MPs. Its viral election campaign - where union members telephone other members and urge them to back Labour - is well organised and well funded.
It is working hard to ensure that its own candidates get selected in safe Labour seats.
For the Conservatives, shadow chancellor George Osborne says: "Gordon Brown cannot have it both ways. He can't condemn the strike whilst at the same time taking money from the strikers' union and while at the same time allowing Charlie Whelan, the political director of that union, to have open access to 10 Downing Street.
"In the end it's a question of leadership for Gordon Brown. He has to cut off the links with the Unite union which is a party within a party now for the Labour Party."
The normally mild-mannered Transport Secretary Lord Adonis was quite irritable in the Lords, accusing the Tories of trying to politicise an industrial dispute
Gordon Brown is certainly aware of the potency of this charge. Six weeks out from a general election, Labour does not wish to be seen as the strikers' friend, a party that takes cash from a union that is causing misery to thousands of holidaymakers.
This is why the prime minister came out so hard to criticise the "unjustified and deplorable" strike action.
The normally mild-mannered Transport Secretary Lord Adonis was quite irritable in the Lords, accusing the Tories of trying to politicise an industrial dispute.
Privately senior Labour sources are distancing themselves from the strike, claiming that it is being driven by the British Airlines Stewards and Stewardesses Association rather than the Unite leadership.
They note too that internal union elections are coming up later this year and wonder if some union officials are setting out their stall.
The sources point out that the Conservatives have been trying to work up a narrative about Labour's links with the unions ever since they were criticised for Lord Ashcroft's tax status and donations.
But note this: the prime minister never actually condemned Unite. He condemned the strike, not the strikers.
There is also a suggestion that both Downing Street and Unite understood that, this close to an election, Mr Brown had no alternative but to be robust.
"The PM's got to do what he's got to do; [Unite leaders] Tony (Woodley) and Derek (Simpson) have got to do what they've got to do," said one Labour source.
And note this too: it is not only the Tories who criticise Unite and Charlie Whelan.
Colin Byrne, Labour's former chief press officer and now senior lobbyist, said: "What the hell is a strike-mongering politically discredited nutter like Charlie Whelan doing at the heart of Labour's election campaign?"
The truth is this: Labour is keen to avoid a politically damaging industrial dispute this close to an election but has only partial influence over the strikers.
The Conservatives are keen to remind voters of Labour's dependence on the unions after enduring weeks of criticism over Lord Ashcroft's role.