Last Wednesday, a quarter to three. The House of Commons. A chill breeze of rumour ripples around the Chamber. Members, in the process of voting, hurry in, asking colleagues on the green benches - what has happened? Someone has been shot, or stabbed? Someone has been hit by a car - is there an attack? On us? Someone hit on the Bridge?

It must be road rage, an accident, a misunderstanding. Shots fired?! The armed police, those courteously consummate professionals, are running in the corridor, telling people to get down, to stay where they are.

The Prime Minister has been rushed out of the voting lobby and away? An attack? Within the Estate? Surely not? Not here, in Westminster, at the heart of our democracy?

The Deputy Speaker, Lindsay Hoyle, a decent, no-nonsense northerner, stands hurriedly to his feet, arms stretched, a strained look on his usually relaxed and friendly face. “Order. I am now going to suspend the sitting. The House is now suspended, but please wait here.”

The day had begun as a typical Westminster day. I attended an early briefing on the Armed Forces, handled constituency casework, attended a briefing on affordable housing innovation, before going into the House for Prime Minister’s Questions. The afternoon brought the Pensions Schemes Bill.

Not something that will set pulses racing, but bringing in further protections for savers; I served on this Bill and was in the Chamber for the debate.

I was not one of those MPs caught in Central Lobby, or in the corridors, as the House’s security swung smoothly into action: blue lights flashing above Churchill arch, doors slamming closed, wooden bars drawn across, bolts clicking shut. Lockdown.

It is sometimes easy, in the cut and thrust of politics, to lose perspective. MPs - even new ones - are used to abuse, or even threats.

It is not, after all, so long since the tragic murder of MP Jo Cox. But this brings it home. An officer has lost his life. Citizens of ten countries - our friends from all over the World - are in critical condition. Blameless pedestrians on Westminster Bridge have been maimed. And so the storms of political strife subside - for a time - for what does the noise count before the cold silence of PC Palmer’s grave? One of those courteous and professional men that I greet in the morning has been lost. One of those who ensure that I can do the job you have sent me to do. He leaves behind a wife and family.

His sacrifice was the epitome of duty and professionalism. The Palace was defended; the attacker did not get more than twenty yards into the estate. Every day the staff of the Palace, the police and all our emergency services do an incredible, and often unsung job. How sad that this was illustrated so vividly, so soon. I pay tribute to them all.

But back in the Chamber, there was some solace. A party of schoolchildren, kept in the public gallery, are singing to keep up their spirits.

They wave at MPs, who wave back. And then it comes. A hush settles over the assembled MPs, asking for news and reading the media on creaking internet - “the Mace, the Mace!” We understand, and silently, we stand. The white-gloved Sergeant at Arms takes the Mace - the symbol of Parliament and the ability to debate the government of the country, freely, peacefully, under the Queen’s protection - gently from the bench and carries it reverently from the Chamber.

Which brings me to my final point: the nature of what you have sent me to Westminster to do.

In my maiden speech I quoted Winston Churchill, born and buried in this constituency, on the nature of what Parliament is about: “to substitute argument for fisticuffs.”

It is tragic that an individual, driven by a perversion of an honourable religion, cannot accept that lesson, but those of us who have been entrusted with the conduct of your affairs will not be cowed. We continue with our business. I spoke in a debate about Equitable Life pensioners on Thursday. The Prime Minister spoke with cool, calm, defiance. I continue to work for you regardless of party or politics. Our work, and our democratic traditions, will continue.

As I left Westminster last week to return to Witney, the flags on the Ministry of Defence outside my office, on the Palace and on the Abbey flew at half-mast. London is mourning, but there is a calm mood of steady defiance. Come what may, the UK’s democracy has been here before. We have prevailed. We will again. Democracy is safe.