Late last summer, Darren Tierney stepped into the newly created role of Permanent Secretary at a pivotal moment for the organisation. In a new episode of Statistically Speaking our host Miles Fletcher sits down with Darren to talk about what happens next.

TRANSCRIPT

MILES FLETCHER

Hello and welcome to another episode of Statistically Speaking, the official podcast of the Office for National Statistics. I'm Miles Fletcher.

Now, if you've followed the UK news much over the past year, you'll know the ONS has been under more scrutiny than at any point in its history, questions about trust, priorities, its core economic data and whether the organisation has simply been trying to do too much at once, have all been very publicly aired.

Today's episode is about what happens next. Late last summer, Darren Tierney stepped into the newly created role of Permanent Secretary at a moment when some of the UK's most relied upon statistics, especially those based on the Labor Force Survey, were under real pressure. In this conversation, we'll talk about Darren's background in government, running large, complex public services and helping to craft and enact key policies. We'll explore how data has shaped his career so far, and what he found when he arrived at the ONS. We'll also dig into some of the hardest questions facing the organisation, and what absolutely has to be fixed first, what may need to stop, how user expectations are being balanced with that and how full confidence in official statistics can be restored. This isn't just an internal reset. What the ONS does and how well it does it matters to policymakers, businesses and the public alike. So join us as we talk about focus, priorities, and the road ahead.

So then Darren, to begin at the beginning, you're not an economist or statistician by profession yourself. What motivated you to take leadership of what is the central organisation in UK statistics?

DARREN TIERNEY

Sure, well look as a non-statistician you can imagine I was a little bit daunted when this prospect first came along for precisely that reason. I was kind of worried that maybe not being a statistician or an economist might be a real drawback but as I thought more about the job, and more about what was needed for the organisation at the time, and with the split of the roles, I thought actually, I can really help. But what really drew me to the role was that although I'm not a statistician, Iv'e been an avid consumer of ONS products for the 25 years that I've been a policy wonk in Whitehall. And going from a good policy professional to a great one, requires both access to good data and also a real understanding of it and knowing how to use it. And it's that background that kind of helped me and really got me into it, and so I saw it as a real opportunity to come and help an organisation that really couldn't be any more consequential for the UK.

MILES FLETCHER

The Devereux review said that what was needed was someone with really serious operational experience, having run serious civil service operations, and you bring plenty of that. Could you just detail some of that? You've had a very strong rise, you know, through the ranks of the civil service. Just trace that for us, if you would.

Yeah. So I started life in what was the old Prescott empire of DETR, which was environment and transport in the regions as a policy wonk working on aviation. I then went and joined the Ministry of Justice, where I spent three years in the private offices of Harriet Harman, Jack Straw and Ken Clarke, and that kind of real frontline policy making, as it were, is the thing that I did a lot of in the first half of my career.

The second half of my career, which is much more relevant to the ONS, was centred around transformation and change. And again, I spent about 12 years or so in the MOJ, and my senior career there was about transforming systems and running big programs. And I went from there to international trade, just after the Referendum, where like a lot of officials at the time, I was quite keen to run to where the energy or the fire was after Brexit. But I didn't fancy working DExEU, and this new department called Trade seemed quite interesting. So I went there, and again, this was a kind of brand new department, and it grew from a few hundred people to about four and a half thousand. And so that kind of building and running the department as a strategy director for investments and exports, I guess those two experiences in justice and trade are the two that I rely on most in this role.

So you spent time in the corridors of power then, the ministerial heights of the civil service, but also having to try and make the machine run efficiently as well, and to deliver public services and achieve policies in the real world. What role has data played in that? And what sort of statistics were you using? What sort of insights were you getting? Can you share some experiences of how that's shaped your career, and your understanding, particularly of the job in hand here at the ONS.

Sure, I guess the job where it was most relevant was when I was in justice, where I worked in civil and family policy, Legal Aid and supporting on prison reform, and particularly on youth justice reform, and maybe that's a good example to pull out. Justice is one of those areas where people have very strong views about what the right policy prescription is, but there's often quite a lack of evidence that goes behind some of these strong policy positions, if I can put it like that, and one of the things that bedevilled us was trying to turn very strong ministerial desire for action across the human justice system into something that was evidence based, and where we could point to proof that these things would work, and we did that several times in the youth justice system.

Perhaps the one that I look back on most fondly in the youth estate...We were constantly telling ourselves, and indeed the world, that kids in the youth estate were getting thirty hours a week of education, and that was true in the sense that that's what we were buying. We were procuring thirty hours a week from providers, but the kids in the estate were not getting thirty hours a week and we didn't really know until we sent in a team of researchers from the MOJ analytical team to do some surveys, and then we also analysed some of the ROI coming out of that estate. And of course, what we discovered was that although we were buying thirty hours of education, it was always being disrupted by all the other services that these kids needed to access. So every dentist, every doctor, every lawyer that was coming in to interact with those kids, that was happening during what would otherwise be the school day, but we didn't really know that. And for years, we were kind of running this system and telling ourselves and indeed telling the world, that this was what was going on, but having analyzed that system and got ourselves some real data we were able to change that system so that it was education first, and all of those other ancillary services would take place outside of the school day. So sometimes it can be quite basic bits of analysis that can result in the biggest changes.

I guess the lesson there is, we always need to never totally trust the data we've got and find better insights and better ways of looking at things. And I guess that leads us into the challenge here at the ONS. What were your first impressions when you took the plunge in, suffice to say, quite interesting circumstances in the earlier part of 2025. What did you make of your earliest days here at the ONS and formulating what needed to be done?

Your characterization of it is right. Before I even arrived, I was talking to a lot of the stakeholders, including Robert Devereux and others, and in doing that and in reading around the issues, I ended up getting quite a negative view of what was going on, perhaps understandably, because that was what was being reported. So I was expecting an organization that was perhaps much more kind of browbeaten than the one I found. And that's not to sound compla...

The road ahead for the ONS: a conversation with Darren Tierney