By his own admission, John Donovan is “truly obsessed”. Standing in his kitchen, the 62-year-old proudly opens the cabinets to reveal shelves stacked not with food but piles of papers and ring binders.

“We don’t cook much,” he said with a chuckle. “Every cupboard in this house has papers in it. It’s the same in my bedroom; the garage is full as well. I have built up so much information so when we put something into print, we can back it up.”

A man obsessed indeed. His modest three-bedroom house in Colchester, Essex, is home to what is probably the world’s largest dossier on Royal Dutch Shell. It also serves as the headquarters for royaldutchshellplc.com, the website where Donovan and his father Alfred – frail but lucid at 92 – pursue a surprisingly effective crusade against the world’s biggest oil company.

So called “gripe sites” are common, especially for companies in highly-emotive areas such as oil, tobacco and banking. Last week Goldman Sachs decided to settle a suit filed against the man who runs a site called goldmansachs666.com after the case garnered celebrity and boosted traffic to the site. The Donovans, though, are more adept than most at inflicting damage on their target.

Their site has become a major thorn in the side of Shell, publishing a relentless stream of insider leaks and negative commentary. It is a remarkable study in the power the internet can have when it is coupled with a couple of industrious individuals with a vendetta.

John estimates that he has published more than 24,000 articles about Shell in the decade and a half since he and his father took their cause online. The website regularly publishes stories, fed to it by a handful of disgruntled executives, which are then picked up by the main-stream press. It has become a hub of activity for antiShell former employees and environmental activists. Last month it had 1.7m hits.

A few weeks ago, for example, it published a plan by new chief executive Peter Voser to slash thousands of jobs before the company was ready to make an announcement. In 2005, when the Kremlin was building a case against Shell over the Sakhalin gas project, the Donovans provided confidential documents regarding alleged environmental infractions directly to Oleg Mitvol, the minister who led the case.

Shell was ultimately forced to sell a stake to the Russians, leading to billions in lost revenue. Mitvol publicly acknowledged the help provided by the Donovans in building his case.

If only Shell knew 20 years ago what it knows now. Back in the 1980s the Donovans had a good relationship with the oil giant. They ran a marketing company that created petrol station promotions for Shell and both sides did well out of the partnership. When a new executive took over marketing, he used several of their schemes but refused to pay for them. So in 1992 they sued. After three legal actions, a fourth ended up in the High Court. In the meantime, Alfred paid people to leaflet Shell’s headquarters on the Thames in central London and they started a pair of antiShell websites.

With legal bills mounting they agreed a “peace treaty under duress” in 1999. It was not the end of the story. Sitting in the cramped study that is the operations centre for the website, John pulls a framed, A4-size oil painting from the wall. It is of Alfred’s former country home that he had to sell in 2000 to pay legal bills. “We had a good life and we had to give our mortgage to our barristers,” he said.

“Perhaps it was a mistake to pursue a case against a big corporation. Maybe it’s my Irish blood but I couldn’t accept it. It changed our lives.” Shell has been paying for it ever since.

In 2007, after the Donovans began airing concerns about safety in the North Sea, internal Shell e-mails admitted that the company was “on the back foot” and needed to “develop a strategy (or options) that puts us in a more positive and secure position” in dealing with the Donovans.

Neither man appears particularly embittered. If anything, they seem quite tickled to be able to give Shell a good kicking. Alfred, a second world war veteran who fought the Japanese in Burma, said: “It’s a laugh.”

Yet what they choose to print doesn’t always fit with their affable demeanour. Last year they published comments by one of their regular contributors who compared a Shell executive to Joseph Fritzl, the Austrian convicted of imprisoning and raping his daughter in a dungeon for nearly two decades. Shell is thought to have considered legal action but decided that publicity would only inflame the situation.

A Shell spokesman said: “The site has a well-known and long-standing agenda. Healthy debate is welcome and encouraged but we choose not to take part if it sinks to the level of personal attacks and innuendo.”

Despite their shoestring budget and minimalist operation, the Donovans are canny operators. When they started up royaldutchshellplc. com in 2005, they incorporated it as a nonprofit site in America, where domain name law is strong. This move served them well. Shell tried to strip them of the site soon after it was opened, labelling them “cyber-squatters”, but the World Intellectual Property Organisation ruled in their favour. The Donovans have since rebooted their two predecessor websites so that the public can access all the information housed there as well.

It is an awkward position for Shell, which was this month crowned by Fortune magazine as the world’s largest company. Trying to shut the website down would draw even more attention to it but letting it continue subjects the company to a constant barrage of negative news, allegations and insults, some of which is picked up by the mainstream media.

In view of Alfred’s advanced age, John does most of the donkey work. He has the time. Unmarried and with no children, the only thing that occupies his time other than the website is his yellow labrador, which he takes for an hour’s walk every morning. He spends six hours a day, seven days a week on the site, fielding e-mails, publishing articles and corresponding with contributors. “It keeps my mind active and I get a kick out of it because we are able to help people,” he said. A nephew helps with the technical aspects of the site. They do not make any money from it and pay just $125 (£77) a month to maintain it.

John doubts that he will ever shut up shop. “There is no ultimate goal,” he said. “We started something and it has grown way beyond what we thought it would. It’s something where people can get revenge on the company or point out things that are wrong. If we can prove it, that’s a real problem for a company like Shell.” In a parting shot he said: “I will continue as long as my health holds up. Since my dad is 92, things don’t look good for Shell.”

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