Bawdon said Lawrence was regarded by many within the legal profession as ‘an icon for justice’, and was ‘an inspiration for legal aid lawyers to keep on doing what they do, despite all the difficulties.’

She reminded the audience at London South Bank University that, although Khan is best known for the Lawrence case, he is actually a defence solicitor, and ‘far more likely to be acting for an alleged murderer than representing the family of a murder victim’. She added that, despite his high profile and the fact that he was involved in ‘one of the seminal cases of the age’, Khan faces exactly the same day-to-day problems of trying to keep his firm afloat and ‘worrying how he can pay the bills, as every other defence solicitor in the country’.

Lawrence and Khan acknowledged that, despite making common cause over justice for Stephen, they still disagree on a great many things, including whether the justice system is skewed in favour of victims or defendants (Khan believes the former; Lawrence the latter); the removal of double jeopardy; and the principle of joint enterprise.

Khan spoke candidly about his experience in the Lawrence case, which has come to define his career.

The failed private prosecution of three suspects, Neil Acourt, Luke Knight and Gary Dobson, in 1996 had been a searing experience, he said – and not one he wanted to repeat. ‘I take my hat off to those lawyers who can prosecute and defend, because you need a completely different mentality to prosecute,’ he said.

As a defence lawyer, he said: ‘I’m very aggressive, I make that absolutely plain, I want to win my cases. I’m an incredibly aggressive defender and I will do what it takes to defend within the ethical parameters.’

But, he said: ‘You can’t do that as a prosecutor; you’re presenting the case on behalf of the state. You are not seeking a conviction, but that’s what I was trying to do in the private prosecution. I will never want to prosecute again because I know what will happen is that I’ll want to win at all costs. So the only lesson I’ve learnt is never prosecute again.’

The six-week trial in 2011, which saw Dobson and David Norris convicted of Stephen’s murder, was naturally difficult for Doreen and Khan, too, found himself looking at the proceedings from a changed perspective.

‘In the past, I’ve represented people who’ve been charged with murder and you know that in the back of the court the mother of the victim is looking at you, with eyes piercing, saying “how dare you put my family through this.” And there I’m sitting next to somebody who’s doing the same thing, and I had to say to Doreen, “Look, that’s the lawyer’s job – it’s not personal”.’

When Doreen questioned why the defence barristers were allowed to lay into prosecution witnesses, all he could do was explain ‘that’s how the system works’.

Khan said that while, for Doreen, the conviction of Dobson and Norris in January 2012 had been about achieving justice, for Khan himself, it was ‘redemption for the failure of the private prosecution’.

He said: ‘To get that result, was in a sense providing that partial justice and redemption for me in relation to that failure. So it was a very selfish thing.’ The decision to bring the private prosecution attracted strong criticism from some in the profession at the time, who thought it a serious error of judgment. Doreen Lawrence stressed, however, that at no stage had she blamed her lawyers when the case collapsed, believing instead she had been let down by a criminal justice system stacked against her.

Khan admitted that however much of an insight the Lawrence case has given him into the plight of victim’s families, it has not changed how he operates as a defence solicitor.

‘I’ve got to do my job. The system is what it is, and you’re not going to get another case if you go soft on witnesses.’

Having looked at the process from both sides now, he finds it difficult, but said: ‘You have to stand there, grit your teeth and carry on. And I’ve done it on many occasions.’

The trial and subsequent conviction of Norris and Dobson was only possible following the scrapping of the double jeopardy rule – which prevented suspects being tried twice for the same crime – and because of advances in forensic science.

The removal of double jeopardy presented a conundrum for Khan, the defence lawyer, whose ‘natural gut instinct’ told him it was ‘intrinsically wrong’ for the law to be scrapped, although he recognised that had it not been changed, Doreen would not have got justice for her son’s death. ‘I’ve got to live with those contradictions.’

Responding, however, to a question from the floor, he admitted that his ‘opposition is diminishing’ and that he accepts there is an ‘increasingly strong argument in favour’ of its abolition, particularly in cases where there is ‘compelling’ forensic evidence.

Joint enterprise in another area where Khan and his most famous client have opposing views. According to Khan the premise is ‘just so wrong’ and needs to be changed.

‘I have been involved in so many cases when 10 or 12 people are in the dock, all facing a murder or robbery charge on the basis of joint enterprise. And you know that many of them didn’t do anything that could be said to be an intention to kill, and yet they’re there and they get convicted on that basis,’ he said. While Doreen wanted to see all present at her son’s killing in the dock.

Overall, Khan believes the criminal justice process is ‘skewed in favour of the victim’. During his career, he says he has seen the defence lawyer’s job get harder. Defendants, he said, ‘don’t get the rights that they should have’, and it has become ‘much more difficult’ to get acquittals.

Rather than give rights to victims, he said the Macpherson Inquiry into Stephen’s death resulted in the defendants’ rights being taken away.

Doreen’s point of view is different. ‘From my perspective the perpetrators have all the rights and that was very clear when Stephen was killed.’

Khan is on record as having said that if another Stephen Lawrence case came across his desk now, he would not be able to take it on due to the impact of successive legal aid cuts. Legal aid firms, he says, have been ‘decimated’. ‘It’s not the profession that I came into,’ he says.

Though he would not want to deter others from pursuing their ‘dreams and passions’ and so would still recommend a new generation of lawyers to go into what he describes as an ‘incredible profession’.

But, he is concerned that that new generation of lawyers is becoming less diverse. Controversially and somewhat reluctantly, he reckons the only way to reverse this is through positive discrimination to help under-represented groups ‘step onto the first rung of the ladder’.

Doreen is also concerned to ensure increased diversity in the professions. The Stephen Lawrence Trust, set up in his memory to give bursaries to architectural students, is being broadened to cover the law.

She would like to be able to do more and get more law firms involved, but to do that, she says the trust needs to raise more funds. ‘We can’t just sit back and allow the legal profession to carry on the way it is going at the moment,’ she said.