Dan Neidle has thrice refused to say how much money he earned in his previous career as a partner at the “magic circle” law firm Clifford Chance. “I’m just not going to tell you,” Neidle, 49, says over flat whites at Compton, a restaurant and cocktail bar in Clerkenwell, London. Asked for the fourth time why he won’t say, given that he now promotes himself as a transparency campaigner, he confesses: “I’m embarrassed. I’m so embarrassed about how horribly overpaid I was that the only person who knows how much I was paid is my wife.” Neidle, who gave up his job as the head of UK tax at Clifford Chance last year in order to work full-time as a fair tax campaigner, says anyone who really wants to know how much money he made can look it up on Google. If you do, you’ll find that the highest paid Clifford Chance partner made £4.9m last year, and its 647 partners each collected just over £2m, on average, a record high. He declines to comment, again, but one is left with the distinct impression that his pay was on the righthand side of the bell curve. Neidle celebrated his pay day by resigning, and setting up a thinktank, Tax Policy Associates. “People take the piss out of me because I clearly don’t have any associates,” he jokes. “The idea [for the name] was [to reflect] that I’m working in association with a whole bunch of different people that have technical expertise in a lot of different areas.” In its first year the one-man thinktank has: Questioned the tax affairs of Nadhim Zahawi in a saga that ended with the Conservative party chair being sacked. Campaigned against and highlighted the unfair treatment of subpostmasters in the Post Office’s Horizon IT scandal Suggested that Premier League football clubs may have avoided paying £250m in tax. Called out retailers failing to pass on the cut in the so-called tampon tax to customers. Forced the Solicitors Regulation Authority to warn the profession against pursuing “abusive litigation” designed to “harass or intimidate” their opponents into silence. Neidle, who studied physics at the University of Bristol and had hoped to become a physicist before finding the maths too hard, said his earnings from Clifford Chance have now given him the freedom to use his tax law expertise to expose wrongdoing and shed light on the unfairness of the tax system. “I worked very hard,” he says of his 23-year career at Clifford Chance in which he rose from trainee to UK head of tax. “But I have plenty of friends who work just as hard, or harder. Teachers, nurses, social workers, doctors, criminal lawyers, I was paid a lot more than all of them. Obviously that is a complicated function of the way society is organised, but I didn’t turn the money away.” Neidle says he was good at his job and his pay was the market rate. “Because I did it, I was free to retire at a relatively early age (48) and have the freedom to do and say whatever I want now. That was the right thing to do for me.” Neidle, who now lives in rural north Norfolk with his wife and children and grows tomatoes in the garden, says choosing what to investigate or campaign about is almost the hardest part of his new career. “I have a long list of 20 things I want to write about or look into,” he says. “I get constant messages from people who vary between well-meaning but addled conspiracy theorists and very smart people who have been investigating and have found something which may or may not be within my bailiwick.” In his old job, picking what to do next was easy. “Whichever client had the most urgent thing, and was shouting the loudest.” In his new role, he’d imagined that most areas of tax policy he did decide to look into would be “really dull stuff” that “only wonks would care about”. But, almost immediately he hit the headlines by questioning an offshore tax arrangement used by Zahawi’s family to hold a more than £20m windfall collected from the sale of his polling company, YouGov. Zahawi fought back against Neidle, hiring lawyers to demand he retract his statements and threaten to sue him if he didn’t. They also warned Neidle against publicly disclosing the content of the letters. Neidle published them on his blog anyway, and tweeted about it to his nearly 100,000 followers for good measure. Eventually, it was revealed that Zahawi had quietly paid a multi-million pound settlement, including a penalty for tax avoidance, to HMRC. Zahawi responded saying the tax body concluded he had made a “careless and not deliberate” error and that his affairs were settled before he became party chair. A review by the prime minister’s ethics adviser advised that Zahawi had made a “serious breach” of the ministerial code by not telling officials he was under investigation by the tax body, and Rishi Sunak sacked him. While he is a member of the Labour party and serves on its national constitutional committee, Neidle says his investigation into Zahawi was not politically motivated. “It wasn’t a crusade at all, it was one of a series of pieces I put out about the Tory leadership candidates and their taxes,” he says. “But [Zahawi’s] reaction was so extreme – I thought, maybe there’s something going on here.” He dug deeper and deeper. Asked again about his politics, Neidle says he has also looked into the tax affairs of Labour politicians. “I’m not partisan. Anyone who knows me, anyone who’s read anything I’ve written will see I’m not a partisan person,” he says. “I have friends who are Tories, I may even have kissed a Tory – not recently. I’ve been married for a long time. “I collaborate, and advise policymakers in five different political parties.” He really did enjoy the battle with Zahawi though, once he’d figured out he was definitely right and felt he could safely ignore the libel lawsuit threats. Lawyers had advised Neidle that if he lost a court battle against Zahawi, it could have easily cost him £2m in costs and damages. “My wife and I thought very seriously about it, because if you really think you’re headed down that path it’s very hard rationally to continue.” After a few days of concern (no sleepless nights though, he claims), Neidle says he was convinced Zahawi was “bluffing”. The stress melted away and suddenly it was “a fun legal litigation game which is what I do. I am a really fucking terrible person to sue, because I enjoy it, I have money, I have time. I have lots of legal friends.”