I joined the Guardian staff on 1 January 1973, the day Britain – with Ireland and Denmark – joined what we then called the Common Market, or the European Community. Forty three years later, I am now leaving the Guardian, appropriately perhaps, given the UK’s own decision to head towards the exit.

The Guardian office in Brussels which I set up was a quiet room in a small flat overlooking Square Ambiorix, close to the European commission and council headquarters. It had a phone and a typewriter, and later a noisy Telex teleprinter, which involved typing into a paper tape. After day-long, sometimes night-long, European talks, you had to wait your turn queuing for a sweaty phone cubicle in a crowded press centre.

Newsdesks could not find you – mobile phones, let alone the internet, didn’t exist. In many ways, Brussels was a journalist’s paradise. The story was, and would remain, both “foreign” and “domestic”, important in terms of UK politics and internationally. Brussels was the HQ of Nato as well as European institutions. It was full of the brightest diplomats from many nations, engaged in almost permanent, often bitter, negotiations with each other and with Eurocrats. It was also full of spies, including MI6 officers who stupidly spent too much time approaching journalists.

For British ministers and officials, used to compliant, even craven, journalists at home, it was a culture shock. The assumption that British journalists would always toe the line was totally counter-productive. If British spokesmen would not tell you what was going on, then a Dutch, French or German one would, with their own country’s spin. The Irish, in hock to Britain and the British market for so long, revelled in embarrassing their big neighbour. Some senior UK officials eventually got the message and gave off-the-record briefings. “But I won’t be briefing when I get posted back to London,” one told me. British officials are more open, the further away they are from Whitehall, he added. He was right.

Brussels was a tremendous source of leaks, and I was the subject of a number of leak inquiries. A Foreign Office document recounts how in 1972 (when I was freelancing for the Guardian and Washington Post), officials “were surprised and irritated by the unauthorised leaking [of a document about eastern European attitudes towards detente in the cold war] to Mr R Norton-Taylor of the Guardian”. The then foreign editor, Ian Wright, phoned me to say that Dennis Greenhill, the top Foreign Office official responsible for liaising with MI6, wanted to know who the leaker was. I sent them on a wild goose chase.

A declassified document at the National Archives notes that on 22 June 1974, the Guardian published a short front-page story about the government’s secret economic forecasts. Harold Wilson, the prime minister, ordered an inquiry, assuming it came from the European commission. The Treasury’s Brussels man, David Hancock, described the leak as “most serious”, adding “Norton-Taylor’s report … would undoubtedly be regarded as a feather in his cap”. Not really. It was what journalists are supposed to do.

From the start it was a battle, a series of battles, between “them”, the continentals , and “us”, the British. It was typified by Reuters’ indefatigable diplomatic correspondent, Mohsin Ali. Indian-born Ali, who as a fomer Hurricane fighter pilot during the war proudly wore his RAF tie every day, began each story with the phrase “Britain today” – followed by such phrases as “warned the French”, or “attacked the Germans”.

Even so soon after we joined the EU, such antagonism, fuelled by newspapers that were hostile from the start, fed an audience – including both left- and rightwing leaders – with stories of wasteful butter mountains and wine lakes, and threats to the British banger. There was no end to such stories. Sarah Helm, then the Independent’s EU correspondent, has described how in the mid-1990s, she was tasked with looking for the kind of stories written by Boris Johnson, then the Telegraph’s Brussels correspondent. “At that time learning about Euro-myths – smaller condoms, square strawberries, fishermen forced to wear hairnets – took up more time than explaining treaty changes,” she wrote.

Helm recalled that many attributed the Danish rejection in a referendum of the Maastricht treaty to a story by Johnson in 1992 – “the biggest whopper of all”, a claim that the then commission president Jacques Delors planned “to rule Europe”. (The Danes accepted it in a second referendum a year later after they secured four opt-outs).

Back in London, encouraged by my experience in Brussels, I started to attack official secrecy, including the blanket ban on any information about the activities of MI5, MI6 and GCHQ. I was unwittingly helped by governments, including the decision to injunct me to prevent the Guardian from revealing the contents of Spycatcher, the memoirs of former MI5 officer, Peter Wright. As a result, I spent six weeks in Sydney covering a hugely entertaining trial. I later witnessed Old Bailey juries acquit the Ministry of Defence official, Clive Ponting, of leaking information about the sinking of the Argentine cruiser, the Belgrano, during the Falklands conflict, and Michael Randle and Pat Pottle of helping the spy George Blake escape from prison. The accused were acquitted even though they admitted the alleged crimes.

And so one epitaph for my time at the Guardian, certainly as far as official secrecy and Europe are concerned, must be, plus ça change.