Tideway taps bond market again with £250M sterling blue bond for Thames Tunnel
What's the deal? Bazalgette Finance plcDealroom has a profile for this one. Try Dealroom →, the financing arm of TidewayDealroom has a profile for this one. Try Dealroom →, has issued a £250 million 6.625% fixed-rate blue bond maturing in 2036. It is the second sterling blue bond from the company behind London's Thames Tideway Tunnel, following its first issuance in July 2025.
What's the endgame? Proceeds fund projects that protect the River Thames from sewage discharges. The tunnel, one of London's largest infrastructure projects, tackles combined sewer overflows into the river and is now operational.
Why now? With the tunnel delivering environmental benefits, this second blue bond is backed by tangible outcomes rather than construction promises. The move marks Tideway's shift from Green Bonds to Blue Bonds as the project transitions from building to running.
The details: The bond was issued under Bazalgette Finance's £10 billion multicurrency programme. To date, Tideway has issued 18 Green Bonds and two Blue Bonds. The company became the first corporate issuer of a sterling blue bond in July 2025.
What's a blue bond? It is a category within Green Bonds, directing proceeds to the sustainable use and protection of marine and freshwater environments. In May 2025, S&P Global Ratings awarded Tideway's Sustainable Finance Framework a Dark Green rating, its highest classification, applying to all bond series under the programme.
The signal: The repeat issuance shows appetite for infrastructure debt tied to clear environmental outcomes. As Tideway moves from construction to delivery, its £10 billion programme points to further issuances — and a maturing market for blue bonds backed by operational assets.
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Image credit: Cristiano Betta
