Twelve years ago yesterday, Britain suffered the worst terror atrocity in its history. But as we remember what happened, certain questions do need to be asked: first of all what happened? Second of all, how was the attack allowed to happen? Third of all, what has changed since that day? And fourth of all where are we now going forwards?

The facts

First of all, we need to deal with the initial question, namely what exactly happened? On the 7th July 2005 fifty-two people died and hundreds were injured, when four suicide bombers attacked the city's transport system.

According to the Metro newspaper, the attackers were named as Sidique Khan, Shehzad Tanweer, Hasib Hussain and Jermaine Lindsay, who "brought horror to the capital". Travelling from Luton, they took a train to King's Cross in London and from there carried out their attacks. With three minutes of 8.50am, attacks were carried out Aldgate, Edgware Road and between King's Cross and Russell Square. A final device was detonated at Tavistock Square at 9.47am. An individual, Gill Hick's, who was caught up with the attack near Russell Square stated that, as the Independent newspaper reported, "You've gone from a bright sunny world...suddenly the bowels of the Earth have opened up".

How did this happen?

As we move on, the second question needs to be asked, principally, how was the attack allowed to happen? This question was covered in a BBC article six years ago. The intelligence agency MI5 had been following a terrorist cell they believed to be involved in the terrorist activities, through the code name, 'Operation Crevice'.

They followed the leader of the cell, Omar Khyam, who they thought was involved in sending money and men to Pakistan. They subsequently followed Khyam and another, Shehzad Tanweer, all the way to West Yorkshire. However, the biggest mistake made was that MI5 did not immediately inform West Yorkshire Police Special Branch that they had followed the individuals.

Further on from this, it was more than four months after Khan and Tanweer had been followed that West Yorkshire had been informed of what was going on. The Special Branch believed that had they been informed and had they been allowed to make arrests, it may well have deterred the attacks from having taken place. But why were they not informed? And this is the critical issue. Because according to MI5, as the BBC reported, it simply "didn't work like that at the time". MI5, it transpired, would only give Special Branch information, on a 'need to know' basis.

What has been learnt?

Moving on from this, let us consider the next question, what has changed since that day? In short, a number of things.

In another report from the BBC, a number of aspects have been highlighted. First of all, bollards have been placed around certain buildings to "absorb the direct impact" of a lorry carrying a bomb. Secondly, MI5 have "increased its presence" around the UK in regional areas. Thirdly, tube communications have increased significantly, especially in the tunnels of the underground. A further change has been the attitude and mentality of the police services, in effect "preparing for the worst". The police and security chiefs are now tasked with thinking through every 'what if', so every eventually is covered. Lastly, the ambulance response has increased greatly. On the day of the attack, medics were late to some of the attack scenes.

Now, there is a "pre-determined response" of any attack that may occur.

Going forwards?

Lastly, where are we now going forwards? What must be stated that in the immediate aftermath of the 7/7 attacks and what happened recently in Manchester and London has been the resolve of the public to not be deterred or affected by what has happened. London Major Sadiq Khan, as the Metro newspaper reported, stated that we as a nation "always pull together" and that "we will never forget those who lost their lives on 7/7". The response from each attack on British soil has been remarkable; in essence, that 'we will never be defeated'. Whilst we look back and remember what has happened, I do hope that the lessons have been learnt from 7/7 and that this sort of attack never happens again.