British ministers, opposition MPs and top civil servants all went to a secretive, corporate-sponsored conference in a luxury hotel in France in January. I’ve pulled together some of the details, but who paid for the conference remains secret — although French energy firm EDF clearly had a big role.

Earlier this year some MPs listed attendance at the January “Franco-British Colloque” in the register of MPs’ interests. The Colloque is a long-running, government-business political conference, like an Anglo-French version of the Bilderberg or Davos conferences. The MPs said they got transport and hotel costs worth £590 each for the conference, so Commons rules meant they had to register the event.

The Franco-British Colloque was founded by BP boss Lord Simon back in the 1990s, and has always been corporate-sponsored. The conference committee invite 50 British and 50 French “delegates” to come debate the big issues. Like Bilderberg, this is where some corporate Establishment “grandees” invite younger political faces. It’s one of the ways business and political elites have a conversation.

However, unlike some previous years, the MPs decided not to say which companies paid for the event. I contacted all the MPs who went, but none would say anything about which corporations sponsored the Colloque, or who else went.

Some of the MPs claimed the Colloque took place in Paris, but the conference was actually held at the Trianon Palace, a luxury hotel in Versailles, just around the corner from the historic royal palace.

Sir Simon McDonald, one of the top Foreign Office civil servants, let slip on Twitter that he was attending the conference. So I asked the Foreign Office under Freedom of Information for details of sponsorship and attendance at the Colloque. They said such details must remain secret because to release such details would be “a breach of confidence and prejudice the interests of the UK abroad.”

The Colloque typically has two “chairs” who help organise the event, one British, one French. I was eventually able to contact the British chair Lord Adair Turner and he was much more open about the conference than any of the MPs or the Foreign Office — but the details he gave are still only partial.

He gave me details of the 50 attendees from Britain — but not the 50 French “delegates.” They include two ministers from the Department of Business, Energy Minister Jesse Norman and Universities Minister Jo Johnson, Charles Roxburgh, the second permanent secretary at the Treasury, three top Foreign Office (FCO) officials — Sir Simon McDonald (FCO permanent under secretary), Angus Lapsley (UK Ambassador to EU Political and Security Committee) and Lord Llewellyn (ambassador to France), Simon Stevens — chief executive of NHS England, Labour MPs Yvette Cooper and Rushanara Ali, Tory MPs Dominic Grieve and George Osborne (who was still an MP then); SNP MPs Tasmina Ahmed Sheikh and Joana Cherry and independent (ex-Ukip) MP Douglas Carswell.

Lord Turner’s list showed Jo Johnson had broken Parliamentary rules because he did not admit to going to the conference in the register of MPs’ interests. I contacted his office and he has since corrected the register — but he neither acknowledged my email or admitted to the error (which is a bit childish).

It seems Energy Minister Jesse Norman did not tell his department he was attending the conference — the Department for Business told me they had no record of his involvement with the Colloque.

This is particularly striking as French energy firm EDF have a history of financing and being involved with the Colloque. Norman is the government’s man on the deal with EDF to build the Hinkley Point nuclear power station — government watchdog the National Audit Office described the plant, which will cost £18 billion to build and will commit the UK to paying £30bn in future “top up” prices, as “risky and expensive.” So any meeting between Norman and EDF is sensitive.

Lord Turner could not say who sponsored the 2017 Colloque — he said only the French chair of the Colloque Pierre Andre de Chalendar, boss of French construction giant St Gobain, could give those details. (Saint-Gobain is incidentally the firm that produced the flammable panels in the Grenfell Tower disaster.)

De Chalendar did not respond to enquiries. However, Lord Turner was able to list the sponsors of the 2016 Colloque, which took place in the UK — it was paid for by four firms, including EDF Energy and Morgan Stanley bank.

The 2017 business attendees included EDF boss Vincent de Rivaz, Morgan Stanley investment boss Frank Petitgas and former MI6 boss Sir John Scarlett, who is now a Morgan Stanley adviser. So both EDF and Morgan Stanley still clearly have a lot of involvement.

Douglas Flint, chairman of HS BC, and Tidjane Thiam, CEO of Credit Suisse, also attended the 2017 event.

Lord Turner described the conference as a mix of “speeches,” “working group discussions” and “roundtable discussions lasting several hours.”

He said the conference broke up into four “working groups” each discussing one of four topics: “UK with or without the EU; Europe with or without the UK,” “Growth, productivity and employment: common and different challenges in Britain and France,” “Fragile or violent neighbours to east and south: military intervention, economic assistance or diplomacy: does anything work?” and “Europe’s migration challenge: can we cope and, if so, how?”

There were also some speeches over dinner: “The speeches were by George Osborne on the Thursday night and by both Yvette Cooper and the French former minister Elisabeth Guigou on the Friday night.”

There was also a “special session” addressed by Amber Rudd (Home Secretary, but formerly energy and climate change secretary) and De Chalendar on “Progress in tackling climate change following the Paris climate change.”

Ministers’ trips are registered at their department, but (as with Jesse Norman) there is no official record of Amber Rudd’s attendance.

The Anglo-French Colloque is like a small, regional sister to bigger business-political conferences like Bilderberg or Davos. Sometimes people develop conspiracy theories around these conferences, seeing them as secret committees of power. These colourful theories are entertaining, but not really credible.

However, these conferences are clearly networking events where elected politicans meet with unelected corporate executives. In this case bankers, former MI6 bosses and nuclear lobbyists mingling with British ministers — so there is a need for transparency. But the MPs and ministers attending the Colloque have broken those transparency rules.