Spring 2005 was when I decided that I would one day work in Lebanon.

I was based in our Paris embassy when Rafik Hariri and 21 others were murdered. I remember reading the powerful reports sent by the then ambassador, James Watt, and sharing frantic updates with Lebanese and French friends. The Valentine’s Day massacre ripped through Lebanon’s political fabric, and robbed Lebanon of a strong and visionary leader. It triggered an extraordinary public response – one in three took to the streets in an outpouring of fury and nationalism. The blast set off a chain of events that got Syrian troops out of Lebanon in the first flowering of the Arab Spring.

I remember feeling shocked by events, inspired by the waves of emotion and political expression, and intoxicated by that beautiful but undefinable sense of hopelessness-defying, odds-battling, freedom-stirring resilience. It was my first real taste of the Lebanese spirit, never to be underestimated. It seemed clear then that Lebanon was going to be a frontline for coexistence. I knew I had to be part of that.

Ten years on, what have we learnt?

The subsequent decade has been a time of tumult, expectation and hope in the Middle East. Also of violence, broken aspirations, and reactionary politics. Too many governments in the region have defined as terrorist anyone who finds themselves in the way of their missiles, chemical weapons, settlements or barrel bombs. Civilians have been caught between the competing narratives of terrorists like ISIL or the terror of dictators, as though these were the only options. Syria is suffering more than any country since the Second World War – this week Assad smilingly denied using barrel bombs against civilians while his army was dropping them on Douma. Some countries have moved forward, some backwards, some have got stuck in a rut. Meanwhile, more people than a decade ago define themselves by religious differences that go back centuries rather than common humanity that goes back millennia. Amid all that, Lebanon is still a frontline in the battle for coexistence.

For some, the assassination will feel like yesterday. Others, a world away. Rafik Hariri’s killers, and those of so many Lebanese, are out there living normal lives. I hope they are haunted by what they did. I hope they are nervous about what the future holds for them. They should be. Because the arc of the moral universe does indeed bend towards justice, however slowly. The Special Tribunal investigating the murder is making painstaking but undeniable progress. These international trials are slow and complex, but we have seen that they should not be written off – ask Milosevic. The Tribunal gives a voice to those who defy impunity. It counters those who claim that unpunished assassinations are simply a price Lebanon has to pay.

We have learnt too that it is hard to fill a vacuum. Rafik Hariri’s murder left a hole in Lebanese politics as well as the capital’s streets. The subsequent departure of the Syrian army also left a hole which no external power has filled. And none should be allowed to. Ten years on, can this be the moment in which the Lebanese can take control of their destiny by choosing their own President? Nobody else can do it. Many of Lebanon’s leaders have concluded that that this vacuum is in their interests. Maybe. But it is not in Lebanon’s.

The rupture of Spring 2005 still defines Lebanese politics today – the dates of the largest demonstrations, 8 and 14 March, gave their names to Lebanon’s two political blocs. Ten years on, it should be clearer than ever that these labels hold us all back. I hope that one product of this tenth anniversary is a stronger sense of the need to move forward together in Lebanon’s interests. The dialogues underway are a tough but vital part of that effort. Some in the region will do what they can to stop them – they should know that we are all watching them.

We have also learnt that this plucky country is stronger than many think. It may have taken some grave threats and deep wounds. Lebanon has too often had its heart broken. But Lebanon is not broken.

When I write or speak about optimism for this region, many tell me that Lebanon is a graveyard of idealism. It has not been a graveyard for mine. And I know from countless conversations how many others still believe that the idea of One Lebanon is far more powerful than any car bomb.

Those 2005 images of hundreds of thousands of cedar flags in central Beirut inspired the world. But some tell me they look at them now and struggle to recognise themselves. I still see in them the spirit that has so attracted me to Lebanon. I hope others feel that too.