Last Updated on September 24, 2026
Finding. On 23 September 2026 Whito checked 59 names linked to UK infrastructure against Companies House. Only 12 were ready to list on the first pass. The rest were parent companies, joint ventures with no registered company, public bodies, or firms with a filing to recheck. Source: Whito, whito.co.uk/infrastructure-companies/research/who-builds-what/, September 2026. Free to quote with a link to this page.
“Infrastructure company” gets used for four very different businesses. Treating them as one leads to wrong answers. A water company is not a builder. A consultancy does not pour concrete. A port owner does not bid for road contracts.
We sort every firm by the work it actually does, not by the word on its website. Below is one checked example from each group.
1. Contractors: the firms that build
A contractor holds a contract to build something and does, or manages, the physical work.
Example: Costain Limited (00610201). Active, incorporated 25 August 1958. Companies House lists its business as roads and motorways, bridges and tunnels, water projects and other civil engineering. HS2 Ltd names Costain as one of the three firms in Skanska Costain STRABAG, which is building the 21km London tunnels from West Ruislip to Euston (HS2 Ltd, 31 July 2026).
2. Utilities: the firms that own the network
A utility owns and runs a regulated network, such as pipes or wires. It hires contractors to build and maintain it. Its regulator sets what it can charge.
Example: Northern Gas Networks Limited (05167070). Active, incorporated 30 June 2004. Ofgem names Northern Gas Networks as a gas distribution network in its RIIO-3 overview (Ofgem, 4 December 2025). Its current named project is a hydrogen storage study at Knapton in North Yorkshire (NGN, 7 August 2026).
3. Operators: the firms that own or run a single asset
An operator owns or runs one asset, or a small set: a tunnel, a railway, a port.
Example: Bazalgette Tunnel Limited (09553573), trading as Tideway. Active, incorporated 21 April 2015. It owns the 25km Thames Tideway Tunnel. On 14 February 2025 Tideway said the last of 21 connections had been made, “bringing the entire system online” (Tideway, 14 February 2025).
4. Advisers: the firms that design, price and check
An adviser designs, plans, costs or manages the work, but does not build it.
Example: Mott MacDonald Limited (01243967). Active, incorporated 11 February 1976, SIC 71129 (other engineering activities). With Jacobs, it is technical partner to Thames Water on the Teddington Direct River Abstraction scheme (Mott MacDonald, 18 September 2024).
What happened to the other 47 names
| Outcome | Count | What it means |
|---|---|---|
| Ready to profile | 12 | Checked, active, one named project with a source |
| Kept for later | 29 | Checked and active, profile not yet written |
| Recheck first | 2 | A confirmation statement date has passed with none listed in the filing history |
| Parent company | 7 | Holding company; shown on the operating company’s profile |
| Dropped | 7 | Joint ventures with no registered company found, duplicates, or out of scope |
| Public body | 2 | HS2 Ltd and National Highways, explained rather than listed |
Update, 23 September 2026. The 29 firms kept for later were profiled and listed the same day, so the directory now lists 41. Two stay held until their Companies House filings update.
Why it matters
If you are checking a firm, the group tells you which register to look at. For a contractor, that means its accounts and safety record. For a utility, it is the regulator. For an operator, it is the concession or licence. For an adviser, it is the professional bodies.
Mix them up and you check the wrong thing.
What AI assistants do with these four groups is a separate question. We put six questions to ChatGPT, Gemini and Google AI Mode on 24 September 2026 and checked every name they gave against the register: who AI names as a UK infrastructure company.
Method and limits
Method. We built a list of 59 names from official pages and firms’ own project pages. Each name was searched on the Companies House register on 23 September 2026. We recorded the legal name, number, status, incorporation date, registered office and any overdue flag shown. One public project per firm comes from an official page or the firm’s own page, linked.
Limits. Companies House shows what a company has filed. It says nothing about the quality of its work or its finances. A missing overdue flag is not proof that everything is filed, and overview pages can lag behind filing history. Joint ventures may be contracts rather than companies, so a missing registration is not a fault. Two firms, BAM Nuttall and Ove Arup & Partners, are held: each has a confirmation statement due date that has passed, the filing history lists none since, and the overview shows no overdue flag. We will recheck them rather than guess. The group a firm sits in is Whito’s judgement from its named work.
Sources, each read on 23 September 2026: HS2 Ltd, 31 Jul 2026 · Ofgem RIIO-3 overview, 4 Dec 2025 · NGN, 7 Aug 2026 · Tideway, 14 Feb 2025 · Mott MacDonald, 18 Sep 2024 · Companies House pages for 00610201, 05167070, 09553573, 01243967.
If a fact here is wrong, tell us and we will check it against the source. Corrections, right of reply and removals: whito.co.uk/corrections/.
All infrastructure research notes · Infrastructure directory
If your business is named here and you think we have a fact wrong, email hello@whito.co.uk and we will check it and correct it. If you want to respond, send us a statement and we will publish it alongside. Full detail: Corrections, right of reply and removals.
