Martin McGuinness's Somme gesture will be rejected by his enemies on both sides
The implications of Martin McGuinness's visit to pay homage to fallen British soldiers in Flanders and the Somme are potentially catastrophic for anyone who wants to be a republican purist and continue alongside him on the political project he has undertaken.
This may not be so easy for a unionist to grasp.
Two prejudices govern many of their perceptions of the IRA.
One is that they were just evil, terrorists, bad people with no principles or humanity. And it is still possible to make that case against some of them.
The other perception, more benign but still denying them political credibility, is that they were young lads back in the Seventies, swept up by events or manipulated by cynical leaders into doing things they would never have done in peaceful times.
Both of these ways of looking at the IRA deny the possibility that they were indeed principled idealists with a strong core belief that they insisted on standing over and were, in some cases, ready to die for.
But that is the truth about many of them, and seen from that standpoint, Martin McGuinness laying a wreath for the dead of the British Army is akin to the Archbishop of Canterbury casting off his finery and dancing naked round a bonfire on Hampstead Heath on Mid Summer's Eve.
There are some things you do not do as an Irish republican, and these are the gestures which undermine every claim you ever made to stand over the principle that Britain was a vicious imperial tyrant that was only to be resisted.
You could argue that he was only doing what the Queen did, and she did it first, when she bowed her head to the dead leaders of the Easter Rising.
In fact, you could argue that her self-effacement was even greater, given that the rebels were self-appointed soldiers of a republic that didn't exist, while the men who died at the Somme were soldiers under orders, serving their country.
That's not how republicans would see it. They would think that the Queen was only doing what she had to do, what she has done in other imperial cast-off countries down the decades of her reign.
Could David Cameron salute Pearse and Connolly? Very unlikely.
Republicanism took its rationale from the understanding that those who went to fight in France served the empire, and the empire was the enemy.
McGuinness's gesture says, in effect, that they have to be seen differently, as good people, brave and self sacrificing, giving their all for their country and earning the respect not just of the British people, but of the Irish rebels too.
This will be a hard one to swallow.
And the precedent of Tom Hartley taking flak for visiting the Garden of Remembrance in Dublin and Alex Maskey attending a memorial for Remembrance Day in St Anne's Cathedral, while establishing that republicans have been a long time inching towards such a gesture, also shows that that they can be excoriated by their followers for making it.
It is a horrible irony for McGuinness that having stretched so far to meet unionism on its own sacred ground, he is still rejected. He might have said it was enough to respect the enemy without offering homage to the dead. Of course, huge numbers of Irishmen, including Belfast Catholics, joined the Army. Some of them even went on to train the IRA, so relations were potentially cordial sometimes at a personal level.
And members of distinctive republican families like the Morrisons and the Gormans joined the British Army. They were not such strangers to each other.
The crassness of those who defaced war memorials and graves this week in Belfast, who daubed the memorial column in Woodvale Park, as others daubed IRA graves in Milltown, is not representative of many people and too much needn't be read into it.
The irony for McGuinness is that while he will be genially thanked by some for what he has done, the significance of his gesture in his own tradition will not be appreciated or reciprocated outside it, and some within that tradition, who do understand the scale of it, will choke on it.