SF wasn't going to let itself misread mood again
The handshake in Belfast became inevitable because there was no handshake in Dublin between Queen Elizabeth and Martin McGuinness when she registered such a spectacular success with her visit last year.
That visit, as everyone knows, could hardly have been better conceived and better handled, with the British and Irish governments pouring such enormous effort into it.
The only people who lost out in Dublin were Sinn Fein, who fell back on the boycott, a tactic they had largely abandoned in recent times. In doing so they excluded themselves from the warm glow of goodwill which everyone else basked in.
Sinn Fein realised right away that they had missed a trick, and that as soon as possible their miscalculation should be corrected. They use so much of the rhetoric of outreach and reconciliation that the politics of boycott today seem lame and outmoded.
Besides, in the peace process they have done so many previously impossible things, and jettisoned so many previously treasured items of republican furniture, that innovation is very familiar to them.
When the queen visited Belfast for her silver jubilee in 1977, the IRA campaign was at full spate, with no talk then of a peace process. It was intent on maintaining what it called its long war, doggedly believing Britain would some day capitulate, collapse and depart, leaving Ireland to its own devices.
The entire republican mindset has changed since 1977: they eventually caught on that Britain and unionism were not going to give in, and that the Republic did not want them to. The logic of this realisation was that the conflict would end not with victory but with a negotiated settlement.
When serious negotiations began the peace process delivered a whole series of unprecedented handshakes and startling moments. One of these came when John Hume, Albert Reynolds and Gerry Adams did a sort of three-way handshake; another came when US President Bill Clinton shook hands with Mr Adams.
Then there was the sight of Mr Adams and Ian Paisley announcing they would go into government together, leading to the spectacle of Mr McGuinness establishing warm personal relations with first Rev Paisley and later Peter Robinson.
In the first phases of the process much of this stuff was absolutely red hot, with Mr Hume in particular coming under savage attack for "consorting with men of violence."
But he, Tony Blair, Bertie Ahern and others stuck with it through repeated crises and upheavals. Mr McGuinness and Mr Adams really were men of violence back then, but Mr Hume's insight was to sense that they might not always be.
The handshake with the queen was the final formal acknowledgement by Britain that Mr McGuinness has shed the shadow of a gunman.
IN politics, Mr McGuinness has displayed personal skills which were not evident in his IRA days.
The handshake was a symbol of reconciliation but not of complete forgiveness, for few can forgive the IRA or the other agencies who took life in the Troubles.
In shaking his hand the queen was acknowledging the journey he and Sinn Fein have undertaken in leaving violence behind.
The queen probably had to steel herself before shaking the hand of the one-time IRA commander. She probably had to make an effort to put the memory of her assassinated cousin, Lord Mountbatten, at least temporarily out of her mind.
It may have helped her to reflect on the thought often repeated by former unionist leader Lord Trimble: that just because someone has a past does not mean they don't have a future.