Mrs Potts, who is 43, and her husband, Jim, a civil servant with the Land Registry, live in a comfortable house in the village of Churcham, a few miles from Gloucester. Anna, at 23 the younger of their two daughters, was a pretty, cheerful girl with long curly hair. She had been married a year, to Brian McGurk, when she was murdered.
She was stalked, then raped and strangled, on 28 August 1991, after she finished her day's work as a clerk with Gloucester City Council and walked to her car in a staff car park. When she didn't come home, her family went out searching for her.
Even at this stage, Mrs Potts had begun to get angry. She says: 'It was the attitude of the police. They wouldn't believe anything serious had happened to her. It was left to the family to search for her. The police wouldn't even lend us torches when it got dark.'
The following morning, Anna's body was found, partly concealed by earth and bracken, on rough ground near Gloucester docks.
Mrs Potts admits that before her daughter's death she was a timid mouse who never complained about anything. Since then she has often sat up through the night firing off protest letters to anyone and everyone who might listen. At the top end of the scale she has written to the Lord Chancellor, the Home Secretary, and the Lord Chief Justice. Locally, she has written to the magistrates' clerk, police chief, head of the probation service and chief executive of Gloucester City Council. Twice she has written to every MP. She estimates she has sent off more than 1,000 letters in all.
Her outpourings have not been in vain. A private member's Bill, currently going through Parliament and expected to reach the statute book shortly, will enable the police and Crown Prosecution Service to challenge a decision by magistrates to grant bail to an alleged offender. The campaign Mrs Potts has waged gave the Bill the poignant thrust it needed to help it through the various stages.
The police soon arrested Anna's killer. Andrew Hagans, 28, was living in a bail hostel not far from the murder scene. At first he denied having anything to do with Anna's death, even though he was seen wearing her necklace and had tried to sell her wedding ring to a fellow hostel-dweller for pounds 10. But, after questioning, he broke down and confessed.
But Mrs Potts's fury mounted when the story of Hagans's background emerged. He had a long history of violent crime, and had been imprisoned for burglary. The Potts family asked what such a man was doing in a bail hostel where, provided he was in at night, he was free to come and go as he pleased.
Hagans, it transpired during his trial, had been arrested for the brutal rape of a 20-year-old woman just 24 days before Anna's death. She said she had been forced into an alleyway and made to perform oral sex with him. He had then pushed her into a ladies' toilet and forced her to have intercourse.
Hagans was found hiding on a rooftop 150 yards away. He claimed sex had taken place with the woman's consent. But witnesses said they heard screaming, shouting and sobbing from the toilets where her bloodstained knickers were found.
Hagans appeared before Cheltenham magistrates and was remanded in custody. Ironically, his cell at Gloucester jail overlooked the car park where Anna left her car each day. After he had been in prison eight days, his solicitor applied for bail. Three magistrates heard the application and, in spite of objections from the police, decided to allow bail after being told there was a place for him at Ryecroft bail hostel, where he would be expertly looked after.
This was when Mrs Potts really exploded. 'Those magistrates were imbeciles for releasing that man. He was allowed out to rape and murder my daughter. They should never sit again in their lives.'
Hagans was sentenced to life imprisonment for Anna's murder, with a concurrent 10-year sentence on the rape charge. But Mrs Potts and her family felt that Anna's death was avoidable, and she resolved that, instead of simply accepting it, she would do something about it.
She says: 'It has had a terrible impact on us. We get up in the morning, still tired after sleepless nights, not caring whether it's raining or sunny. Some mornings I feel all right for a little while: then it's like a bubble suddenly going 'plop', and it all comes back. The effect on poor Brian was terrible. He went to pieces and he wasn't able to help our campaign.
'But I had this anger churning away inside me. It gave me an energy. I realised there must be scores of men like Hagans prowling around who have been allowed their freedom by soft magistrates. They are a danger to us all and should remain locked up until their trials.'
A Northumbria Police study showed that 40 per cent of detected crime was the work of those on bail, albeit that the vast majority of offences were burglaries and car crime.
Kay Potts's first salvo of letters brought only disappointing results. From the Home Office came a refusal to hold a public inquiry into the circumstances of Anna's death. Mrs Potts also put in an official complaint about the police's handling of the case. A police constable had seen Hagans loitering near the car park and actually checked and searched him. Mrs Potts says: 'At first the police assured us that the constable had ordered Hagans to leave the car park. This turned out not to be true. At the trial the constable said that after searching him he had not asked Hagans to leave. It seemed as though they wanted to shut us up.'
She also complained to Anna's employers about the security of the car park. 'Somebody had actually seen Anna being marched off by her killer - but done nothing,' says Mrs Potts. 'He said he thought it was her boyfriend, but he admitted later she was walking strangely - as you would with a knife held against your back.'
So the family decided to take a more militant approach that would put them in the public eye. They organised a demonstration near the place where Anna was killed. They carried banners and distributed handbills. Mrs Potts made a speech attacking lax bail laws. She said: 'Me, speaking in public] I was too shy even to take part in the school play. It was as if somebody else was making that speech and I was watching her. It was the anger that enabled me to do it.'
The next stage of the campaign was to write to every member of Parliament. Anna's sister Helen brought a group of the murdered girl's friends to the Potts's house and they spent a couple of evenings folding letters and putting them in envelopes.
One of the recipients was Michael Stephen, the Conservative MP for Shoreham. A former barrister, he was chairman of the backbench legal affairs committee. He too was unhappy about the bail laws, and was planning a private member's Bill to change them. Mr Stephen said: 'The letters Mrs Potts wrote to members informed them of the tragic events that led to Anna's death, and it meant a very large number of them supported my early day motion. Without this support, the Bill would not have got through.'
Mr Stephen hopes his Bail (Amendment) Bill will become law before the end of the current parliamentary session. The police and Crown Prosecution Service will then have the right to appeal if magistrates grant bail against their advice. This right is already enjoyed by the Procurator Fiscal, head of the independent prosecution service in Scotland, and is frequently used. The accused person remains in custody until the appeal is heard.
Such a law would almost certainly have saved the life of Anna McGurk. Kay Potts says: 'I do feel I've achieved something by helping to get the bail law changed. It's helped me as well. Without positive things to do, I don't think I could have coped. It won't bring Anna back, but it might prevent some other poor girl suffering the same fate.'