My wife and I first met Dominic Raab, the foreign secretary, on 9 October. Our 19-year-old son, Harry, had been killed two months earlier, when his motorbike was involved in a crash with a car. The driver of the car was Anne Sacoolas. She claimed diplomatic immunity – her husband is a US intelligence official – and fled the country. We were trying to push for her return to the UK – by the time we met Mr Raab, at the Foreign Office, we were desperate for news of any progress.

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We had been led to believe that the meeting would be helpful, and that Mr Raab would have good news for us. We were not told what the good news might be but we imagined he was going to tell us that she was going to come back for questioning, or that there was at least a plan to make that happen.

But the meeting was terrible. Mr Raab was cold, stiff and impersonal. He offered his condolences, yet they only came across as empty words. The worst of it was that he didn’t actually have any good news: he insisted that Anne Sacoolas had diplomatic immunity. Charlotte, my wife, asked him if he would put in another request for a waiver and he said he would do that.

I had allowed my hopes to build up, and now I realised we had been brought in on false pretences. It felt to us like a publicity stunt so that Mr Raab could make it look to the public as though he was doing something for us. After we left the meeting, I broke down outside his office. I have been furious with him ever since.

A couple of weeks later, in the House of Commons, Mr Raab made a statement that completely contradicted what he told us at the meeting on 9 October. He said that on 8 October, the day before we met him, the US and UK had agreed that the question of diplomatic immunity was no longer pertinent because Anne Sacoolas had left the country. As a result, there were no longer any obstacles to justice. Why, then, had he told us that she still had immunity? When we heard that statement, we were horrified. After that, there was no way we could trust him.

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Again and again, Mr Rabb and his cabinet colleagues have told the country that he is doing everything he can to assist us. In an interview with Sky News last month, he said he was trying to clear the path to justice – even though he claimed, a month earlier, that there were no obstacles. That was when we realised that this man says things that he thinks will please the public, but has nothing to back them up.

We have not heard from Mr Raab at all since our meeting with him. We have made several public appeals for him or anyone in authority to come and talk to us. He has never given me any contact details for getting in touch with him directly.

That is why we decided to travel down to a hustings in Mr Raab’s constituency, Esher and Walton, last week. I am desperate for justice for my son. If Mr Raab wasn’t going to let us know what he was doing, I wanted to ask him face to face, so he could explain all the lengths he had supposedly gone to. We also wanted to meet local voters and let them know precisely what was going on. We think politicians should be honest and decent, and we feel Mr Raab is neither of those.

He seemed really troubled to see me at the hustings. He was rude and dismissive, he pointed his finger at me. He could have easily pulled me aside and talked to me. If he didn’t have time to speak, he could have arranged for us to meet another time. Instead, he wouldn’t even shake my hand.

We are now suing the FCO over its absurd decision to advise Northants police that Anne Sacoolas had diplomatic immunity. We have brought this case not only for Harry, but for everyone in the country. The US and UK governments are ripping up the rule of law and that affects each and every one of us. Today, during Donald Trump’s visit to the UK, we are protesting outside Buckingham Palace in an attempt to make ourselves heard.

All we want is for Anne Sacoolas to return, so she can face the consequences of her actions that night when she took my Harry’s life, and for the truth in this whole mess to come out. I am not aware of a single cabinet minister who has called publicly for her to be returned. That is shameful. It’s hard to escape the conclusion that the British authorities care more about preserving the relationship with the US than looking after the rights of citizens like us.

• Tim Dunn is the father of Harry Dunn, a 19-year-old motorcyclist killed outside a Northamptonshire RAF base