Alder Castle, constructed in the late 1990s in the City of London, is an eight-floor L-shaped office building with approximately 90,000 sq ft of accommodation. The building sits adjacent to the Grade I listed Church of St Anne and St Agnes and borders the London Wall - a Roman defensive wall dating to c. AD 200, now a Scheduled Ancient Monument.

As with many buildings of this era, Alder Castle required updating to meet contemporary workplace expectations. Morrow + Lorraine were appointed to enhance the entrance and reception experience, upgrade commuter facilities, provide outdoor amenity spaces, and deliver CAT A office space. This focus on improving occupier amenity through enhanced facilities for wellness, collaboration and access to external landscaped areas reflects the practice's wider commitment to bringing older buildings up to date with current workplace trends.

Additional massing was added at the corner,  while preserving sight lines to safeguard views of the listed church. This increased the entrance footprint and created outdoor amenity space on upper levels. The extension was integrated with the existing elevational detailing by extending the corbel datum line to form a canopy and using a consistent material palette.

A key aspect of the design approach was continuing the landscaped setting around the listed church into the building itself. New balconies were designed to encourage planting across the facades, creating a harmonious relationship between the historic churchyard and contemporary intervention.

For the double-height reception interior, the design approach centred on a carefully considered material palette of oak, plaster, terrazzo and bronze. Continuity is maintained throughout with the use of natural materials and thoughtful warm lighting, creating a space that feels both grand and welcoming.

The primary challenge centred on creating a geometrically complex extension that appeared integral to the original building within stringent planning constraints. The project demonstrates how thoughtful intervention can modernise older office buildings while respecting historic context - increasingly valued by landlords seeking to future-proof their assets.