Gilts: Stagflation Risks the BoE Can't Ignore

UK long-term gilt yields averaged 4.45% in January 2026, down from the 4.69% peak in September 2025. That decline looked like the start of a durable trend — the BoE had cut rates, inflation was falling, and the fiscal picture was stabilising. March has shattered that narrative.

The 10-year gilt has pushed back above 4.6%, erasing four months of progress in less than two weeks. Compare this with US Treasuries: the 10-year note sits at 4.21% as of March 11, with the 2-year at 3.64%. The UK-US 10-year spread has widened to roughly 40 basis points — a premium that reflects the UK's worse inflation arithmetic and weaker growth trajectory.

The UK government's fiscal headroom — the buffer between planned borrowing and its fiscal rules — was already razor-thin at £9.9 billion before the Iran conflict. Rising gilt yields directly erode that margin because higher borrowing costs feed straight into debt interest projections.

Every 25 basis point rise in gilt yields across the curve adds approximately £6-7 billion to annual debt servicing costs. With around a quarter of UK government debt linked to inflation (index-linked gilts), a simultaneous rise in RPI and nominal yields creates a double hit to the public finances.

Chancellor Rachel Reeves faces an ugly trade-off. Higher energy prices simultaneously push up inflation-linked debt costs, reduce tax revenues through weaker growth, and increase welfare spending. The OBR's March forecast will likely revise fiscal headroom sharply lower, potentially forcing spending cuts or tax rises that further dampen growth.

Gilt issuance plans for 2026-27 already call for over £250 billion in gross financing. If investor appetite weakens — and the September 2022 mini-budget demonstrated how quickly gilt markets can seize up — the Debt Management Office may need to offer higher yields to clear auctions. That self-reinforcing dynamic is exactly what gilt bears have been warning about.

The US yield curve spread at 0.51% — positive but narrowing — suggests American recession risks are rising too. A synchronised US-UK slowdown would normally be bullish for bonds, but not when the cause is an inflationary supply shock rather than a demand collapse.

Gilts at 4.6% are offering the highest nominal income in over a decade outside the brief 2022 crisis spike. For long-term income investors, this is not a disaster — it is an entry point. But timing matters enormously.

The BoE's March 19 decision is the next catalyst. A hold — now the overwhelming consensus — would confirm the market's repricing and likely stabilise yields near current levels. Any hint of future cuts being pushed to H2 2026 or beyond could send the 10-year above 4.7%. Conversely, a surprise cut (improbable but not impossible if data softens rapidly) would trigger a sharp rally.

Short-duration gilts (2-5 year maturities) offer a better risk-reward than long-dated bonds here. They carry less interest rate sensitivity, and if the BoE does eventually resume cutting — even at a slower pace — the front end of the curve will benefit first. The 2-year gilt yield is pricing Bank Rate staying around 3.5-3.75% for the foreseeable future, which already reflects a cautious BoE.

For UK investors holding long-dated gilts or gilt funds, the key question is whether this is a temporary geopolitical spike or a regime change. The answer depends almost entirely on oil. If the Iran conflict de-escalates and Brent crude drops back below $80, gilt yields could retrace to the 4.2-4.3% range within weeks. If oil sustains above $100, the BoE's entire 2026 easing path is dead, and gilts will need to reprice further.

The base case: gilts remain under pressure through Q2 as the inflation data absorbs higher energy costs. The BoE delays its next cut to May or June at the earliest. Long-term gilt yields settle in a 4.3-4.7% range, higher than the market expected three weeks ago but sustainable if the economy avoids outright recession.