CoStar Data Shows London Demand for 4 Star Offices Topping 40% in the City Core despite Top-Quality Space Shortage

London City Core office demand increased, while vacancy for best-in-class space fell to 2.1%, according to CoStar. The Square Mile represented over 42% of Central London demand for 4-Star offices so far in 2026, versus 18% for 5-Star offices.

Analysis

The investable signal is a widening split within London offices, not a blanket office recovery. Scarcity in top-tier City space can support rent and occupancy at prime assets, while demand concentrated in 4-Star space suggests tenants may be prioritizing location and value over the most expensive specification. That can benefit owners of well-located, lettable stock—but it may leave older buildings exposed to refurbishment costs and weaker leasing even as headline prime vacancy tightens. The second-order constraint is deliverable supply: if conversions, upgrades, or new construction are slow, existing prime landlords gain bargaining power; if upgrades require substantial capital, asset quality alone will not guarantee attractive returns.

Near term, the data may lift sentiment toward London offices, but a single market snapshot does not establish durable net absorption or pricing power. Over 1–3 months, verify signed leasing, effective rents after incentives, tenant move-outs, and the development/refurbishment pipeline. Over 6–18 months, the key divide is likely to be prime assets with credible energy and amenity standards versus secondary space facing capex and obsolescence. The release does not provide landlord-level exposure or financial outcomes, so a broad sector long is not justified. The thesis weakens if incentives rise, leasing converts into relocations without net absorption, or new/refurbished supply materially eases scarcity.

Key Decisions for Investors

• Keep UK office exposure selective rather than buying the sector: screen Landsec and British Land for verified City prime-space exposure, lease expiries, and refurbishment commitments before taking a position.
• Potential relative-value setup: favor landlords with scarce, lettable City assets over owners concentrated in secondary offices, but wait for confirmation in effective rents and leasing volumes; do not infer company-level earnings upside from market-wide vacancy data alone.
• Set a 1–3 month diligence trigger around CoStar follow-up data and landlord updates: look for net absorption, rent-free periods/incentives, new completions, and tenant retention. Rising incentives or weak net absorption would invalidate the scarcity-to-rent thesis.
• Avoid extrapolating the 4-Star demand share into a broad upgrade cycle: the 5-Star comparison may reflect affordability or tenant mix, and the release does not establish that tenants are expanding rather than relocating.