Willmott-Brown was an ex-army officer and he arrived in Albert Square in March 1986 as the new area manager for 'Luxford and Copley', the brewery that owned The Queen Vic. By December of that year he had decided to move to the square and he bought Debbie Wilkins' house at 43 Albert Square when she was forced to sell it following her fiancé, Andy's, death. He and Debbie later had a fling, but it didn't progress into anything serious. Pat Wicks took a shine to him and attempted to seduce him on several occasions, but was rebuffed each time. During the early years he became friendly with Colin Russell.
By February 1987, Willmott-Brown decided to give up his job as brewery manager and he purchased an old pub in disuse in Turpin Road named The Dagmar, which he refurbished as a new suave wine-bar. Local publican Den Watts was furious to have competition for his pub, The Queen Vic, and he was even more angry to discover that his wife, Angie (from whom he had recently separated), was the manageress of The Dagmar.
The Dagmar opened for business in June that year and the competition between the two pubs began. They competed with each other for best decorated pub in 'The London In Bloom' competition, they were pitted against each other in a five-a-side football match and they continuously tried to poach each other's staff. However the following year the Dagmar began to lose business. The residents of Walford never really took to the upper-class establishment and he was now in competition with not only the Vic, but Strokes winebar too, which was being managed by Den after he gave up tenancy at the Vic. It was at this time that Gregory Mantel (a member of the criminal organisation known as The Firm) came on the scene and tried to force James to allow his company, 'Walford Investments', to buy into the business. James refused, and as a result none of his usual creditors would trade with him. The business severely suffered. His ire with Den escalated when he discovered that he was in league with the Firm, and he reported him to the police for shady dealings at Strokes winebar. However his conversation with the police was overheard by his barman, Simon Wicks, who informed Den. When the residents learnt that James had 'grassed' to the police, no one would enter his bar. His business was now in financial ruin and James became frantic and slightly erratic under all the pressure.
After Kathy had an argument with Pete one night, Wilmott-Brown invited her back to his place for a glass of wine after work, but when it became clear that he was trying to seduce her, she attempted to leave. However, he wouldn't take no for an answer, the situation got out of hand and what began as seduction ended in rape. Den discovered Kathy in an emotional wreck. When he realised what had happened he sought out his contacts within the Firm, Joanne Francis and Brad Williams, and demanded retribution. He soon watched with glee as a fire-bomb was thrown into the deserted Dagmar and it exploded into flames. Unfortunately for Den this act would eventually lead to his imprisonment and attempted murder, after The Firm expected him to take the rap for the arson and later decided they wanted him dead.
When Willmott-Brown returned days later, he was mortified to see his business burnt down. He was also met with extreme hostility from everyone on the square. Den threatened him, as did Kathy's niece, Michelle, so he fled to his lawyers to get legal advice. Upon his arrest, Willmott-Brown countered Kathy's claims by suggesting that Kathy consented to sex, and that it was common knowledge that the two were having an affair. He suggested that Pete was a violent man and that Kathy made up the rape to avoid his wrath. He also claimed that Kathy's bruises were merely a result of their rampant sexual encounter. Willmott-Brown thought he had done enough to fool the police and he was stunned when they formally charged him with rape.
He stood trial in April 1989, but not before he'd attempted to bribe Kathy to drop the charges against him. Kathy lulled him into believing that she was ready to take his hush money, only to betray him straight into the hands of D.I Bob Ashley, who was secretly listening next door. Kathy was forced to relive the rape at James' trial and was relieved when he was found guilty and imprisoned for three years. However, Pete was unable to live with what had happened to his wife, and their marriage ended soon after.
Upon his release in January 1992, Willmott-Brown returned to the square, and proceeded to try and buy the flats that Grant and Phil Mitchell were selling. He was planning to move back to Walford and set up another business, so he sent Kathy a tape telling her that he wanted to meet her at the hotel he was staying at in Hampstead. He promised that if she objected he would disappear and never return.
His return sent shockwaves around the square and Pete organised a mob to track him down at the same time that Kathy planned to meet him. Kathy got there first and after listening to Willmott-Brown's tale of the hardship he faced in prison and how much he had changed, she pleaded with him to leave the Square for good and never return. Despite his past promise, however, he would not agree to leave Walford. Kathy then left feeling repulsed and cheated, but unbeknown to her, Pete had also arrived at Willmott-Brown's location to enact his revenge. Pete and his mob forced him into their car and drove him to Pete's highrise flat building, where Pete threatened to throw him off the top unless he signed a paper stating that he would sell out of Walford and never return. Immediately after, Willmott-Brown phoned his solicitor and took out an injunction on Pete, but proceeded to move to the Square. He continued to send Kathy tapes confessing his undying love for her.
Eventually Kathy and Pete went to confront James at his house and he and Pete nearly came to blows. An emotional Kathy was finally able to relay her hurt and anger over the rape she was subjected to and she expressed her fury at James for never once apologising for the act. James protested that they had something truly special, but after a heated conversation Kathy managed to make him see how deluded he was being by showing him the destruction he'd caused her and her family. In a bid for attention James threatened to commit suicide by taking an overdose of tranquillizers, but Kathy stopped him, refusing to allow him to get off the hook so easily. James then finally apologised to Kathy for raping her, and begged for her forgiveness. Kathy was pleased he was sorry, but wouldn't forgive him, feeling her forgiveness would give him permission to stop being sorry and she told him she was never going to do anything he asked, ever again, not even that. The confrontation and the apology finally allowed Kathy the closure she needed. Defeated, James then left Walford and has not been seen since.
In 1994, Kathy began to have recurring nightmares about Wilmott-Brown, so her boyfriend, Phil Mitchell, went in search of him. He tracked down James's wife, and found out that he was back in prison after being convicted of raping another woman. Nothing more has been heard about him since.