Are UK defence stocks overvalued?

Everyone agrees defence budgets are rising. That agreement is exactly the problem: a consensus gets into the price. Here is how to value a contract-backed business, and what to check before paying for a narrative.

By Nathan Wickham-Hurd · Founder, Oak Growth · First-class Economics & Finance, MBA · Last reviewed August 2026

Context, August 2026. Expectations of higher UK defence spending firmed after Andy Burnham became Prime Minister and John Healey, the former Defence Secretary, was appointed Chancellor. No commitment to 3% of GDP by 2030 has been made. Defence shares had already risen a long way on the spending narrative before that, and several UK names have gone sideways over the past year despite it. Market conditions change; the framework below is meant to outlast them.

The gap between a good story and a good price

Defence is the clearest example in the UK market of a sector where everyone agrees on the direction of travel. Budgets are rising across NATO, order books are long, and the political risk of cutting spending is high. None of that tells you whether a share is worth buying today, because a consensus view gets into the price.

The evidence for that is in the returns. Several UK defence names have delivered flat or negative twelve-month share price performance while the spending narrative kept improving. When a stock stops responding to good news, the market is telling you the good news was already discounted — and the next move depends on delivery, not announcements.

How to value a defence contractor

Start with the order book, not the P/E

Defence earnings are contracted years ahead, which makes the backlog a better anchor than a single year's profit. Compare the order book to annual revenue for a rough measure of visibility, and check whether it is growing faster than revenue — a backlog that shrinks while revenue rises means today's earnings are consuming tomorrow's.

Cash conversion, because contracts distort profit

Long-term contract accounting lets a company recognise profit on work in progress before the cash arrives. Compare cumulative operating cash flow with cumulative net income over five years. Persistent divergence is the single most useful warning sign in this sector, and one that historically preceded trouble at more than one UK contractor. See free cash flow.

Margins are capped by design

Government customers negotiate on cost-plus terms and audit the result. That produces reliable but modest margins and limits how far return on invested capital can rise. If you are modelling margin expansion of the kind a software business might achieve, you have the wrong mental model for the sector.

Single-customer concentration

A defence company's moat is real — security clearance, decades of programme knowledge, certification barriers no newcomer can cross quickly. But it is a moat around one or two government customers whose budgets are set politically. That is a durable moat with a concentrated risk sitting inside it, and the discount rate should reflect that.

Programme timing risk

Multi-decade programmes slip. A delayed submarine or aircraft programme moves cash flows several years to the right, and in a discounted cash flow that reduces present value materially even when the total contract value is unchanged.

The specific mistake to avoid right now

Buying a cyclical or thematic sector after the narrative is universally accepted, at a multiple that assumes the narrative continues, leaves you no margin of safety. That is not an argument against defence companies — several are genuinely high-quality businesses. It is an argument for insisting on the same discount you would demand anywhere else, rather than paying up because the direction of travel feels obvious.

The reverse risk is real too: if peace breaks out, defence shares fall on the headline even though multi-decade procurement commitments rarely reverse quickly. Both directions are opportunities for someone who has done the valuation work in advance and knows what they think the business is worth.

Which UK names sit in this sector

The listed UK exposure is concentrated: a large prime contractor, a naval and nuclear engineering group, a countermeasures and sensors specialist, a defence technology and testing company, and an aero-engine maker whose naval nuclear propulsion arm sits alongside a civil aviation business. That last point matters — several of these are not pure plays, so a defence thesis buys you a second business you may not have analysed.

Check the numbers behind the narrative

Oak Growth scores FTSE 100 and FTSE 250 companies on moat, management, economics and value, with an estimated intrinsic value and margin of safety for each — so you can see whether a sector story is already in the price.

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Common questions

Are UK defence stocks overvalued in 2026?

Some may be. Share prices across the sector rose sharply on the expectation of higher NATO and UK budgets, and several UK names have since moved sideways despite further positive spending news — a sign that a lot of the story is already reflected in prices. Whether any individual company is overvalued depends on its order book, cash conversion and price against estimated intrinsic value.

How do you value a defence company?

Anchor on the order book rather than a single year's earnings, since revenue is contracted years ahead. Check that reported profit converts into operating cash flow, accept that government contracting caps margins, and apply a discount rate that reflects concentration in one or two political customers.

Will UK defence spending rise under the new government?

Ministers have signalled that national security ranks among the highest spending priorities, and the appointment of a former Defence Secretary as Chancellor was read by markets as supportive. No commitment to 3% of GDP by 2030 has been made, and industry executives have publicly argued current commitments fall short.

Are defence stocks a defensive investment?

Not in the usual sense. Revenue is unusually visible because it is contracted and government-funded, which is genuinely stabilising, but valuations move sharply with geopolitical headlines and programme announcements. Visible revenue does not mean a stable share price.

Also see: Undervalued FTSE 100 stocks → · What is an economic moat → · Margin of safety →