On 7 July 2005, I shared an Edgware Road tube carriage with a radical Islamist. I survived his attack, and the company I shared in that single tube train has been good to me ever since. And that is what I remember every time I hear about a new terror attack on ordinary people going about their daily lives.

On 7/7 the tube bombers struck at 8:50am. I was four stops away from work. I lost a leg in the ordeal, but I survived. I remember thinking later that a small mercy was that it was only adults caught up this attack and that, at the age of 50, I was one of the oldest affected. But yesterday’s horrible events in Westminster involved children and students, and that thought hit me hard.

As a survivor of terrorism, this week’s attack certainly affected me. I barely took in the news at work in the afternoon, glancing up at the screens in the office, and the Evening Standard that I read on the bus home was out too early to catch the news. But at home, there followed the grim rolling news on the various channels. My son Matthew, only 20-months-old on 7/7 and now aged 13, was sent home early from his school not too far from the terrible scene.

Parliament holds a minute-long silence in memory of the victims of the Westminster attack

I have always said my experience on 7/7 helped me to empathise with others caught in similar circumstances. I am certainly better equipped to deal with and comfort the dying and the bereaved. Yet watching the coverage of the attack last night, my experiences prompted two feelings.

The first was a terrible sadness and empathy and love for all those innocents, those who died and their bereaved who will never forget them, and those who have been brutally injured. Some I suspect, like me, will be seriously injured. Though this is initially a terrible experience to endure, they will be shown love and will be supported, as I was too.

Fellow travellers with me on that day of 7/7, some injured themselves, stayed on that carriage. They helped and prayed for those who died, and tended to those who survived in the 45 minutes before the paramedics arrived. I still keep in touch with my particular saviours and with other amputees and injured victims. We meet up every 7/7, also with the paramedics, prosthetists and police who helped us that day, who got us walking again, who became part of our lives.

In pictures: Westminster attack Show all 9 1 /9 In pictures: Westminster attack In pictures: Westminster attack An air ambulance lands after gunfire sounds were heard close to the Palace of Westminster in London PA wire In pictures: Westminster attack MPs wait until the situation is under control in Westminster. 'The alleged assailant was shot by armed police,' David Lidington, leader of the House of Commons, told the house. BBC News In pictures: Westminster attack Crowds gather in Westminster after shooting incident, which police are treating as terror attack BBC News In pictures: Westminster attack Police were also called to an incident on Westminster Bridge nearby AP In pictures: Westminster attack Early reports indicate the car, which mounted the pavement on Westminster Bridge and mowed into around a dozen people, was the same vehicle which then rammed into the railings of the Palace of Westminster, just around the corner Reuters In pictures: Westminster attack Security sources described the suspected assailant as a middle-aged Asian man, who is understood to have left the car before attacking a police officer with a seven-to-eight inch knife PA wire In pictures: Westminster attack Police have asked people to avoid the immediate area to allow emergency services to deal with the ongoing incident AP In pictures: Westminster attack One woman has died and a number of others, including the police officer, have been hurt, according to a junior doctor at St Thomas' Hospital Reuters In pictures: Westminster attack At least three gun shots were heard by those inside Westminster, and proceedings in the House of Commons have been suspended AP

The second feeling was one of great respect and understanding for all the emergency services who responded at Westminster. It was very obvious yesterday that they arrived at the scene very quickly and worked with courage and efficiency. I have a great admiration for them.

The family liaison officers in the police were very supportive of my wife on 7/7 itself, and of me and the family later. I am grateful for one of the police who helped me in the carriage before the emergency teams arrived. I am alive because of one paramedic who tended to me after nearly an hour of losing blood (we named our daughter, born in 2008, after her). I am constantly grateful to the teams at St Mary’s and Stanmore hospitals who put me back together again.

I relate all this because I see, and I know, that dedicated public servants will do their good work for the innocents caught up in the events yesterday. The love that I saw seemed to outweigh the hate. After my days in intensive care my wife relayed to me all the good wishes and prayers there had been, how it brought together people from around the world – including from South Africa, where I was born.

Last night, similarly, I heard from my sister in New Zealand and a brother in Australia asking after us and “thinking of you all in London”.

(David outside Edgware Road Tube Station)

Of course the scourge of terror will always resonate with me. It makes me sad, but I always know that goodness does show itself at the same time. A part of me cries at the terrible things done to innocent civilians, but a part of me hopes people know that there is more love in the world.

I have in the years since 7/7 been proud to speak to my experience, eschewing politics and generalisations of those responsible; I speak as a survivor thankful to all those who showed love. My speeches always used to say that since 7/7 there thankfully hadn’t been an event like that in London again – but the murder of Lee Rigby and now yesterday’s attack on Westminster show what a hard task our security and emergency services have.