Four European public-sector open-source programmes get cited constantly in the same breath, as though they were one movement moving at one speed. They are not. One has been running for seventeen years and has published cost figures verified by the European Commission. One is most of the way through a 30,000-workstation migration. One is a directive whose founding document has not been published. And one is a pilot that its own ministry publicly scaled back.
Sorting them by evidence rather than by headline gives a much clearer picture of what open source in government actually delivers, and what it takes.
France's Gendarmerie: the strongest evidence available
The Gendarmerie Nationale has run a Linux desktop environment continuously since 2008. By June 2024 it had reached 103,164 workstations, around 97 per cent of the force's computing estate.
The reason this case carries more weight than the others is the source. The European Commission's IDABC and Open Source Observatory programme published a case study on it, which makes the figures a matter of institutional record rather than vendor or advocacy claims.
Those figures are worth stating precisely, because they are frequently quoted loosely. The 2009 estimate, covering the full cost base, put annual savings at €7 million. The narrower post-2014 figure, covering licensing costs alone, is €2 million a year. From 2013 onward, the Gendarmerie has sustained a 40 per cent reduction in total cost of ownership.
Seventeen years of continuous operation at six-figure workstation scale is the single most useful data point in this entire subject. It establishes that the model works at national scale over a long horizon, which no pilot can demonstrate.
Schleswig-Holstein: the migration currently in progress
The German state of Schleswig-Holstein is moving approximately 30,000 state administration workstations from Microsoft Office 365 and Windows to LibreOffice and Linux, driven by Digital Minister Dirk Schrödter and framed explicitly as digital sovereignty.
As of December 2025, the state government reported approximately 80 per cent of state administration workstations migrated to LibreOffice, excluding tax administration. The email component finished earlier, on 2 October 2025, moving more than 44,000 mailboxes to Open-Xchange and Thunderbird.
On cost, the state government's own figures are €15 million in annual licensing savings against a one-time investment of €9 million in 2026 for final migration and open-source infrastructure work.
Two things about those numbers deserve care. They are the state government's claims rather than an independent audit, which is normal for a programme still in progress but worth stating. And the €9 million is only the 2026 tranche, not the total programme cost since inception, so it is not a complete payback calculation.
What makes Schleswig-Holstein valuable is that it is happening now, at scale, with progress reported publicly as it goes. The completed email migration in particular is a discrete, verifiable milestone rather than an aspiration.
France's government-wide directive: reported, not yet documented
On 8 April 2026, DINUM, France's interministerial digital directorate, was reported to have required government ministries to migrate around 2.5 million civil servants' workstations away from Windows and to reduce dependence on eight categories of American software spanning productivity, collaboration, cloud infrastructure and databases.
That would be the largest public-sector migration ever attempted in Europe by a wide margin.
It should be treated carefully for a specific reason: the primary government document has not been published. As of August 2026 the circular or ministerial instruction establishing the mandate is not publicly accessible. Every detail in circulation comes from consistent media reporting rather than from the authoritative text.
Consistent reporting is not nothing, and the Gendarmerie's seventeen-year record is exactly the domestic precedent such a directive would rest on. But the scope, the timetable and the obligations cannot be verified until the document appears. Anyone planning around it should say so.
Denmark: smaller than the coverage suggested
Denmark's Ministry of Digital Affairs announced a pilot in June 2025 to test moving from Microsoft Office 365 to Collabora, an open-source platform based on LibreOffice. Minister Caroline Stage Olsen set it out in a Politiken interview on 10 June 2025, and the ministry published the official announcement on 19 June 2025.
The international coverage that followed described a ministry leaving Microsoft. The ministry's own position is narrower.
On 24 June 2025 the Digitaliseringsministeriet issued a clarification stating that the project is much smaller than first described and that there are no concrete plans to completely phase out Microsoft within the ministry. Windows remains in use; the pilot concerns office productivity software only. It involves a group of the department's employees, with no participant numbers disclosed, and no cost figures have been published.
That is a considerably more modest thing than the headlines conveyed, and reporting it accurately matters. It is positioned as a first step within Denmark's four-year digitalisation strategy for 2025 to 2029, in which digital sovereignty is a stated priority across national, regional and municipal planning for the first time. As a signal of direction it is meaningful. As evidence of savings or feasibility it does not yet carry weight.
What is the UK doing instead?
The UK took a consolidation route, and it has published more evaluation evidence than any of the four programmes above.
Crown Commercial Service announced the Strategic Partnership Arrangement 2024, or SPA24, on 21 October 2024, effective from 1 November 2024. It is a five-year memorandum of understanding with Microsoft replacing the three-year Digital Transformation Arrangement 21, and it covers Microsoft 365, Azure, Business Applications and, for the first time in a UK government agreement, Microsoft 365 Copilot.
On spend, the most reliable public statement is a parliamentary written answer given by Georgia Gould MP, Cabinet Office Parliamentary Secretary, in July 2025. Circulating five-year totals differ from one another, and the Cabinet Office has confirmed that some published figures combine the final months of DTA21 with SPA24 activity, so a single headline number should be treated with caution.
The more interesting UK material is the evaluation work. The government published a cross-government Microsoft 365 Copilot experiment findings report in June 2025, and the Department for Business and Trade published its own Copilot evaluation in August 2025. Publishing structured evaluations of a major deployment, positive and negative, is not something the other four programmes have matched, and it is genuinely useful evidence for any organisation weighing the same tools. We have covered the practical end of this in getting Microsoft 365 Copilot working for a 20-person UK company without an enterprise agreement and in stopping Copilot surfacing confidential data to the wrong people in a 365 tenant.
It is also worth noting that the UK already has open-source policy on the books. The guidance at Be open and use open source on gov.uk, alongside the Open Standards Principles, asks departments to give open-source solutions equal consideration and to avoid vendor lock-in. The core guidance was last updated on 31 March 2021, with departmental policies refreshed more recently. The policy framework exists; SPA24 is a commercial arrangement made within it.
What would a UK department actually learn from these programmes?
Office productivity is the tractable piece; the operating system is harder. Every one of the four programmes started with, or limited itself to, the productivity suite. Denmark stopped there deliberately. Schleswig-Holstein got its email migration done as a discrete milestone before the desktop was finished. Even the Gendarmerie took years to reach 97 per cent. Sequencing matters more than ambition.
Budget for the transition, not just the licence saving. Schleswig-Holstein's €9 million for 2026 sits against €15 million of annual savings. That ratio is the honest shape of these programmes: real savings, real up-front cost, payback over years rather than months.
Long-run operation is where the evidence is thinnest and most valuable. The Gendarmerie is the only case with a seventeen-year record and an externally documented total cost of ownership figure. Anyone building a business case should weight it accordingly and treat pilots as directional rather than probative.
Check what a programme actually covers before citing it. Denmark is the clearest lesson here. The gap between the coverage and the ministry's own clarification was substantial, and a business case built on the coverage would have been built on sand.
Watch the regulatory backdrop. The CMA concluded its cloud services market investigation on 31 March 2026, accepting commitments on switching, egress and interoperability, and its work examined Microsoft's software licensing practices directly. Those commitments change switching economics for every UK buyer, and we have set out what they change and when each piece takes effect.
For organisations at a smaller scale weighing the same questions, our guides to open-source software for small UK businesses and self-hosted alternatives cover the practical options, and how UK providers fit into government cloud frameworks sets out the procurement routes.
Sources
European Commission IDABC and Open Source Observatory, case study on the Gendarmerie Nationale's migration to Ubuntu — the workstation numbers, the €7 million full-cost annual estimate from 2009, the €2 million licensing figure post-2014, and the 40 per cent total cost of ownership reduction sustained from 2013.
Landesregierung Schleswig-Holstein, State Chancellery press releases — approximately 30,000 workstations, the €15 million annual licensing saving and €9 million one-time 2026 investment, approximately 80 per cent LibreOffice migration as at December 2025 excluding tax administration, and completion of the email migration of more than 44,000 mailboxes to Open-Xchange and Thunderbird on 2 October 2025.
Digitaliseringsministeriet (Danish Ministry of Digital Affairs), official announcement of the digital sovereignty pilot project, 19 June 2025, and the ministry's clarification of 24 June 2025 that the project is much smaller than first described with no concrete plans to completely phase out Microsoft. Minister Caroline Stage Olsen's interview with Politiken, 10 June 2025.
DINUM, Direction interministérielle du numérique — the reported directive of 8 April 2026 covering approximately 2.5 million workstations. The primary circular or ministerial instruction was not publicly available at the time of writing and the details derive from media reporting.
Crown Commercial Service, Crown Commercial Service signs memorandum of understanding with Microsoft UK (SPA24), 21 October 2024 — the five-year term, the 1 November 2024 effective date, the replacement of DTA21 and the inclusion of Microsoft 365 Copilot.
UK Parliament, written answer by Georgia Gould MP, Cabinet Office Parliamentary Secretary, July 2025, on government Microsoft spending.
GOV.UK, Microsoft 365 Copilot experiment: cross-government findings report, June 2025, and Department for Business and Trade, Microsoft 365 Copilot evaluation, August 2025.
GOV.UK, Be open and use open source guidance and the Open Standards Principles — the requirement to give open-source solutions equal consideration and to avoid vendor lock-in.
National Audit Office, Efficiency in government procurement of common goods and services (July 2024, HC 116) and Government's approach to technology suppliers: addressing the challenges (January 2025).
Competition and Markets Authority, Cloud services market investigation and the actions announced on 31 March 2026.
