No choice but to shake Queen's hand, Martin
Sooner or later it was bound to happen, where some high ranking political figure representing Sinn Fein, would be confronted with the problem, of being obliged to share political detente, with a member of the British monarchy, in this case no less a person than the Queen herself.
In every facet of life, one sooner or later, is obliged to shake hands with people they have no time for, nor even like, and I have little doubt that includes the Queen.
This 'shaking of hands' takes place every day, between so-called friends, (myself included) political enemies, opposing politicians, heads of state throughout the world.
For Sinn Fein to create an impasse of not meeting the Queen, does nothing for the progress of of Ireland's unity. It would be a backward step, viewed I suggest, with deep disappointment from Sinn Fein's political friends in places like the US etc.
Did not the Sinn Fein Lord Mayor of Cork shake hands with the Queen on her visit there last year?
The Pope shakes hands with the head of the Anglican faith, Putin shakes hands with Obama, etc, so I say to Martin shake her hand. Nobody forced you into the position you now find yourself in, but shake her hand you must, if you wish to ever unite this country.