The hedge fund industry's main trade body has warned the Bank of England that proposed changes to a key part of the UK bond market's plumbing could make things worse in a crisis, not better. In a letter reported by Reuters, the Alternative Investment Management Association (AIMA) said that expanding central clearing and imposing minimum haircuts on gilt repurchase agreements, or repos, could reduce liquidity and add volatility exactly when markets are under stress.
For everyday investors, this is about how smoothly the UK government bond market functions. Gilts are the bonds the government issues to borrow money, and they sit at the heart of the UK financial system. When that market seizes up, it can ripple through pensions, banks and even mortgage rates. So a debate about technical rules in the repo market is not just an obscure regulatory spat — it has real consequences for anyone with savings or a pension.
What is a gilt repo?
A repo is essentially a secured loan. One party borrows cash and pledges gilts as collateral, agreeing to buy them back later at a slightly higher price. The difference in price is effectively the interest paid on the loan. Repos are core market infrastructure: they let investors finance bond positions, help dealers manage their inventories, and keep the whole system liquid.
The Bank of England is consulting on reforms to this market after two recent episodes when UK bond markets were stressed enough to require central bank intervention. The first was the 2020 “Dash for Cash” at the start of the pandemic, when investors rushed to sell everything, including gilts, and funding markets froze. The second was the 2022 liability-driven investment (LDI) crisis, when a surge in long-dated gilt yields forced pension funds to dump bonds quickly.
The two big ideas on the table are expanding central clearing — routing more trades through a clearinghouse that collects margin from both sides — and setting minimum haircuts on trades that stay outside clearing. A haircut is a buffer: the borrower must post more collateral than the loan amount, so if the value of the gilts falls, the lender is still protected.
Why AIMA is worried
AIMA argues that these steps could make funding more demanding and less flexible. If haircuts are set at a fixed minimum, lenders may be less willing to accept certain collateral or extend longer-term repos. That could nudge hedge funds away from the typical two-week repo and into overnight borrowing, where positions must be refinanced every single day.
That shift matters because of the scale involved. Bank of England data suggests hedge funds account for about £85 billion of gilt repo borrowing. If their funding becomes more fragile, a small shock could quickly turn into a bigger problem. In stressed markets, margin and haircut demands often rise — clearinghouses and lenders want more protection as volatility climbs. That means borrowers need to come up with more cash or high-quality collateral at the worst possible time.
If funding shifts toward overnight repo, the pressure hits faster. A position financed overnight must be rolled over daily, so even a brief pullback by lenders can force leveraged traders to shrink their holdings. That can mean selling gilts into a falling market, widening bid-ask spreads and pushing yields up further — a dynamic that often shows up most at the long end of the curve.
What it means for investors
For most people, this is not about hedge funds themselves. It is about the stability of the UK bond market, which underpins everything from pension fund returns to the cost of government borrowing. If the reforms make the repo market safer on paper but less resilient in practice, the next crisis could be messier than it needed to be.
The Bank of England's goal is understandable: after two near-misses, policymakers want to reduce the risk of another funding freeze. But AIMA's warning highlights a classic regulatory trade-off. Rules that make individual trades safer can, in aggregate, make the system more fragile if they push activity into less stable corners.
Investors should watch how the consultation unfolds and whether the Bank of England adjusts its proposals. The debate also echoes similar discussions in other markets, where regulators are grappling with how to make clearing and collateral rules work without choking off liquidity. As Treasury yields ease and central banks hold steady, the focus on market plumbing may seem distant, but it is precisely these quiet reforms that determine how well the system holds up when the next storm hits.
For now, the key takeaway is that the repo market is not just a technical sideshow. It is the grease that keeps the bond market moving. If that grease dries up in a crisis, the effects can be felt far beyond the trading desks — in pension funds, in borrowing costs, and ultimately in the wider economy.
