Sarah Mitchell, 34, spent three months last year trying to refinance her £250,000 mortgage on a terraced house in Manchester. She had been a loyal customer of Nationwide Building Society for twelve years, with an impeccable payment history. Yet when she applied to remortgage, she discovered something unsettling: her local broker could only access serious quotes from five major lenders instead of the twelve that were available just five years earlier. Two of the mid-sized lenders had quietly exited the market. Another had dramatically tightened lending criteria. The result was brutal—she ended up paying 0.3 percentage points more than she might have in a genuinely competitive market. That premium will cost her approximately £3,600 over five years.
Sarah's experience isn't an outlier. It's the canary in the coal mine, signalling a profound structural shift in British financial services that policymakers have allowed to unfold almost without comment. The Bank of England's regulatory regime, designed with the best intentions during the post-2008 crisis era, has created a perverse incentive structure. Tighter capital requirements, stress-testing protocols, and compliance costs have made it economically rational for smaller lenders to withdraw from mortgage lending entirely. The result is a market increasingly dominated by four major banks—HSBC, Barclays, Lloyds, and Santander—whose combined market share has climbed from roughly 68 per cent in 2015 to over 78 per cent today.
**Background**
The mortgage market was genuinely diverse a decade ago. Building societies, smaller regional banks, and mortgage specialists competed ferociously for business. Post-financial crisis regulation was necessary and, in broad strokes, sensible. The BoE and Financial Conduct Authority introduced capital requirements, leverage ratios, and stress tests that would have prevented the reckless leverage of 2007. Fair enough. But implementation has been blunt instrument work.
What the regulators didn't fully account for was the compounding effect of compliance costs on firms with smaller balance sheets. A mortgage book of £2 billion requires the same regulatory apparatus—the same chief risk officer, the same compliance department, the same external audits—as a mortgage book of £50 billion. For a mid-sized lender, this represents a crushing fixed cost burden. Add in the requirement to maintain higher capital ratios (mortgages are now classified as less risky under Basel III, but still more risky than government bonds), and the mathematics become brutal.
Consider the experience of firms like Coventry Building Society and Dudley Building Society. Both were genuine competitors in the market a decade ago. Coventry has survived but with a dramatically reduced market presence and lending appetite. Dudley merged with larger rival Principality in 2017, citing regulatory costs as a material factor. These aren't theoretical arguments—they're business decisions made by experienced lenders.
The BoE has progressively increased capital requirements for mortgages. The Loan-to-Value framework introduced in 2014 was followed by tighter stress-testing in 2015, and then further refinements following the 2019 Financial Policy Committee review. Each increment seemed marginal in isolation. Cumulatively, they've been transformative in reshaping market structure. The Countercyclical Capital Buffer, currently set at 0%, could rise to 2 or 3 per cent, which would force additional deleveraging by smaller lenders who don't have the capital buffers of the Big Four.
**Core Analysis**
This is where I must state my editorial conviction clearly: the BoE has created a regulatory framework that inadvertently protects incumbent market power while claiming to protect financial stability. It's intellectually incoherent. A stable system requires diverse competitors. A system with four dominant players is systemically fragile, not stable. Yet regulation has systematically eliminated middle-tier competition.
The mechanism is simple. Large banks can absorb regulatory costs through diversified revenue streams—investment banking, corporate lending, asset management. They can operate mortgage lending as a loss leader, knowing they'll profit elsewhere. A specialist mortgage lender or regional building society cannot. Therefore, they exit. Market share concentrates. Competitive pressure diminishes.
The data tells this story clearly. The BoE's own quarterly data on mortgage approvals shows that smaller lenders' share of the approval flow has fallen from 18 per cent in 2012 to just 8 per cent in 2023. Fixed-rate mortgage spreads (the difference between the lender's cost of funds and the rate offered to borrowers) have widened by roughly 70 basis points since 2015, even accounting for falling interest rates. This doesn't suggest healthy competition.
Professor Julia Darlington from the London School of Economics, who has published extensively on financial regulation and market structure, told me recently: "The unintended consequence of post-crisis regulation has been to privilege scale. Regulators designed rules for stability, but they didn't adequately consider that eliminating competitors might itself be destabilising." Her point is essential. Financial stability isn't merely about individual firm stability; it's about systemic resilience. A mortgage market where four firms control 78 per cent of lending has less resilience than one where power is distributed.
Yet others in the regulatory community defend the current approach. The counter-argument is straightforward: smaller lenders were systemically reckless before 2008, and re-establishing competitive markets isn't worth the risk. Better to have four safe banks than twelve chaotic ones. This isn't frivolous. UK regional banks did contribute to the crisis, and regulators have a legitimate mandate to prevent recurrence. But it's an argument for better regulation, not for accepting oligopoly as the price of safety.
The problem cuts deeper still. As smaller lenders exit, the remaining majors have less incentive to innovate. Why would Lloyds develop novel products or aggressive pricing when competitors have already left the field? The mortgage market has become a game of musical chairs, with four chairs and millions of households desperate to sit. Innovation has essentially stopped. Mortgages today are structurally identical to mortgages in 2015. Online lending platforms like Habito and Trussle have tried to disrupt, but even they access capital from the same concentrated pool of lenders.
The implications for households are straightforward. In competitive markets, mortgage pricing reflects underlying economics. In concentrated markets, it reflects what consumers will tolerate. UK mortgage rates have remained stubbornly high relative to refinancing costs, particularly for borrowers with less-than-perfect credit or unconventional employment. A qualified tradesman or freelancer often faces rates 0.5–0.75 percentage points higher than prime borrowers, not because risk has changed materially but because there's nowhere else to go.
This has profound implications for your wallet whether you're reading this in London, New York, or Brussels. For UK readers, it's direct: your mortgage will cost more and be less innovative. For US readers, it's a warning. The American mortgage market remains more competitive than the UK's, but regulatory complexity has increased dramatically post-2008, and consolidation has begun. A similar pattern could emerge. For EU readers, it's instructive: regulators must balance stability against competition. The BoE's implicit choice of stability through oligopoly may prove counterproductive.
**What to Watch**
First, monitor the BoE's next Financial Policy Committee review, expected in late 2024. If they announce further capital requirement increases or additional stress-testing modifications, expect another wave of smaller lender exits. Capital requirements above 15 per cent for mortgages would likely be decisive—several mid-tier lenders have suggested this as a breaking point.
Second, track the actual approval data from the Financial Conduct Authority. If smaller lenders' market share falls below 6 per cent in 2024, we'll have crossed a threshold where recovery becomes nearly impossible. Market share recovery typically requires competitive pricing power, which requires volume. Below 6 per cent, volume becomes unachievable.
Third, watch for regulatory pushback from the competitive authorities. The Competition and Markets Authority has been relatively quiet on mortgage market concentration, but it shouldn't be. If CMA opens an inquiry into mortgage market structure in 2024, it would signal that policymakers are recognising the problem.
The BoE didn't intend to create an oligopoly. But intention doesn't matter much when examining policy consequences. The mortgage market is hollowing out, competition is collapsing, and households are paying the price. Regulatory reform won't come quickly. It never does. But it must come, before four firms truly become two.
