London had a glimpse of the hateful ideology that Christians in Iraq and Syria know all too well

The Prime Minister, in her statement in the aftermath of yesterday’s attack, defiantly insisted that parliamentary business would today continue as usual. During the morning sittings in both Houses there was a united and wholly unambiguous message that those who would destroy our democracy and fundamental freedoms will not succeed. But in the sombre atmosphere that inevitably prevailed, it wasn’t quite business as usual.

And we always need to remind ourselves that this is not the first, and will not be the last attack on Westminster – both on the buildings and on the values which are its foundation stones.

Nearly 40 years ago, on March 30 1979, on the day after I was elected to the House of Commons in a by-election, Airey Neave was murdered by the Irish National Liberation Army. He was blown up just yards from where PC Keith Palmer – a father of two and a member of the parliamentary and diplomatic protection squad – was yesterday murdered by an Islamist terrorist.

Keith had worked at Westminster for 15 years and he was one of our gallant band of men and women who protect us and every day greet us, and endless visitors, with great courtesy – but who also know that Westminster is far more than a tourist attraction.

It is an iconic building that stands for democracy and freedom and is therefore bound to be a target for those who wish to destroy those things and impose hate-driven ideologies.

PC Palmer’s body lay just yards from the entrance to Westminster Hall, which was subjected to Nazi bombs at the height of the Second World War.

In 1940 a high explosive bomb fell into Old Palace Yard. In 1941 an incendiary hit the Victoria Tower and a police sergeant showed great courage when he climbed the scaffold and extinguished the burning magnesium with a sandbag. Then the western courtyard was hit and two auxiliary policemen were killed.

Next, the Commons Chamber – built by William Rufus in 1097 – was hit along with Westminster Hall. As the Commons burned, firemen with axes broke down the doors of the Hall, and as the medieval rafters went up in flames they pumped in water from the Thames to save the Hall.

PC Palmer stands in a long and heroic tradition of extraordinary bravery placed at the service of their country.

If the walls of Westminster Hall could speak they could tell this nation’s history – of its struggles for political and religious freedom, its belief in human rights and its belief in the rule of law.

From its construction in 1097, and the first meeting of Parliament in 1265, to the trials of William Wallace in 1305, of St Thomas More in 1535, and Charles I in 1649, to the lying-in-state of kings, queens and prime ministers, there is little that this Hall could not tell us about who we are and what we stand for as a nation.

My first visit to Westminster Hall was in 1965, as a schoolboy, when we came to pay our respects to Sir Winston Churchill, whose body had been brought to the Hall and whose leadership saw this country through its darkest hours.

Yesterday, after being locked down for several hours in Central Lobby, many of us were taken into the Hall, where hundreds of people waited as events continued to unfold.

Here were peers, MPs, secretaries, researchers, ancillary and catering staff and visitors to the House – the complete diverse mix that makes up the Westminster community on any working day.

I wondered what some of the schoolchildren, who had been singing songs to keep up their spirits, would make of this, their first visit to Westminster. Beyond the tragedy I hope they will be inspired and realise that in every generation the baton must pass to the one that follows.

As the attack was taking place I was meeting the Egyptian Coptic Bishop Angaelos. We talked about recent attacks on Coptic Christians in Egypt, many driven out by ISIS killers from the Sinai Peninsula. We talked about the Copts who had been murdered by ISIS in Libya, who went to their deaths refusing to renounce their faith. We recalled that the last time we had been together was to stand outside Westminster Abbey at a service of remembrance to mark the deaths of 25 people at Cairo’s Cathedral of St Mark.

Then one of our Doorkeepers urgently asked us to follow him and he took us to Central Lobby. Among many we spoke to there was Lord Tebbit, who had survived the Brighton bomb and whose dear wife Margaret had been paralysed by the attack.

Bishop Angaelos and I spent five hours in the lockdown in Central Lobby and Westminster Hall. This was unpleasant, but nothing in comparison to what happened outside.

At 4.00pm I had been due to chair a meeting on North Korea and I still don’t know if anyone hoping to come into the House for that hearing was hurt. I do know that South Koreans were among the casualties on Westminster Bridge. The intended speaker, who had escaped from North Korea, and his translator sent me a text to say that they had gotten safely away.

This morning I arrived at the House at 7.30 am to prepare for a meeting I was due to chair on the Committee Corridor about the plight of Christians in Erbil, who had escaped from ISIS genocide in Iraq and Syria.

The meeting had been organised by the charity Aid to the Church in Need. They had flown over Stephen Rasche, who leads the humanitarian and resettlement programmes for more than 70,000 displaced Christian families in northern Iraq.

Although we were unable to get members of the public into the building, we went ahead with the meeting and Mr Rasche spoke to peers such as Baroness (Helena) Kennedy QC, Lord Hylton and Lord Gordon, and he met the international development minister, Lord Bates.

Mr Rasche’s visit comes at a critical time for Christians in the wake of the expulsion of ISIS from the Nineveh Plains, the region of northern Iraq which for centuries had been home to Catholic and Orthodox communities as well as other minorities. What sort of message would it have sent to them if that meeting had to be cancelled because of Islamist terror on the streets of London?

It’s almost a year since the House of Commons voted to declare events in Iraq and Syria to be a genocide against Christians, Yazidis and other minorities.

Stephen Rasche said the programmes he organises on behalf of Chaldean Archbishop Bashar Warda of Erbil are running out of medicine, food – and hope. He described what it is like to live every day under the shadow of terror: “Christians are hanging on as a people – just barely,” he said.

He pointed out that British aid simply doesn’t reach those we have said are facing genocide because it goes into UN camps which the minorities would be too frightened to stay in, as many of those who persecuted them are in those very camps.

Without help “medicine will run out in 40 days, food in two months.” Without help no one from these ancient communities will be left: “we will become custodians of a caretaker culture”

They are praying for the day when it will be safe to return to the Christian villages of Nineveh Plain and Mosul – but meanwhile they are a people whose story is written in mass graves, enslavement, rape and torture.

Yesterday, London had a glimpse of the brutality and unforgiving hatred that fuels this global ideology.

But, as Justin Welby, the Archbishop of Canterbury, reminded us when we assembled in the House later in the morning, hatred need not win.

Westminster has withstood far worse, and in displaying traditional British stoicism and resilience, Parliament must also inspire and encourage beleaguered communities, the world over, by displaying leadership and determination in resisting those who would destroy the values for which PC Palmer gave his life.

David Alton (Lord Alton of Liverpool) is an independent crossbench peer