Conversion of office building to luxury residential home
Sector
›
Developments
Value
›
£2.2m
Location
›
Westminster, London

In this record
We acquired an office building on Old Queen Street in Westminster for £2.2 million. Close to St James’s Park, the property had an exceptional location but was underused in its existing form.
We saw the opportunity to reposition it entirely, creating a residential scheme that would stand out in London’s emerging luxury market.
Over the course of a four-year project, we invested £4.5 million in a comprehensive conversion.
This involved adding a new top floor with curved glass doors overlooking the garden, as well as reconfiguring the interiors to create flowing, liveable spaces.
Every element was carefully considered, from bespoke lighting designed by Sally Storey, to furniture supplied by William Yeoward, and gardens curated by Terra Firma Landscapes.
Conservation architects Donald Insall Associates led the design, ensuring that the building’s period character was preserved while introducing modern touches.
The scheme was also notable for its innovative details. We installed dumb waiters linking the kitchen to the dining areas, maximising convenience and efficiency. The new interiors blended practicality with sophistication, and the house was finished to a standard that few properties in Westminster could match at the time.
Before the eventual sale, the property was rented to a high-profile musician, with Savills describing it as “the best house in London to let.”
The project was successfully concluded with a sale price just under £9 million.
Old Queen Street ably demonstrates how we bring together vision, market awareness and execution.
It highlighted our ability to anticipate demand in the ultra-prime London residential market at an early stage, while working within complex planning and design frameworks.
And most importantly, it showed how an under-utilised office building could be reimagined by us as a one-of-a-kind home, delivering both strong returns and a distinctive addition to the city’s housing stock.
(Image credit: Beauchamp Estates)
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An underused Westminster office became a one-of-a-kind luxury home, acquired for £2.2m and sold close to £9m. If you hold a well-placed asset that no longer earns its keep, it may be worth reimagining.
Key insights
Real estate sits alongside equities, private equity and fixed income in most family office portfolios – but it behaves differently to all of them, and that's exactly why it earns its place.
Real estate is one of the core asset classes in most family office portfolios, alongside public equities, private equity, fixed income and increasingly private credit. Family office asset allocation to real estate has grown in recent years, driven by its long-term yield, its role as a diversifier against public markets, and its suitability for multi-generational holding periods that few other asset classes match.
Family offices typically hold a mix of private equity and direct investments, real estate, public equities, fixed income and alternative investments, with the exact split varying by size, generational stage and risk appetite. Real estate tends to justify its place in that mix for reasons other asset classes don't share: a steady, long-term income yield; a long holding horizon that matches how families think about multi-generational wealth; and enough direct control that a family can shape an asset's performance rather than simply hold a position and wait.
Once real estate earns its place in the allocation, there's a separate question of how to access it – directly, or through a fund or REIT structure. That decision affects fees, control and liquidity in more depth than an allocation discussion needs to cover; the trade-offs are set out in full in our guide to financial planning for property investment. What matters at the allocation level is simpler: direct ownership is what lets a family actively shape a property's performance rather than passively hold a position in it, which is a large part of why real estate earns a place in the portfolio in the first place.
Discovery Park in Kent is a clear illustration of what that control can achieve. Brought under active management, the science park's capital value grew from around £20m to more than £75m over two years – restructuring leases and separating out service charges rather than simply holding the asset and waiting. A passive fund position, with no say over how the asset is run, couldn't have delivered the same outcome.
UK real estate remains a core allocation, but the mix within it is shifting. Portfolios are diversifying into student accommodation, retail parks and leisure assets alongside the more traditional office and residential holdings, and branded hotel and hospitality assets remain in favour where they carry a strong covenant. Family offices weighing new allocations are also factoring in wider considerations earlier than before – joint venture and asset management arrangements, transparency requirements such as the Land Registry's Persons of Significant Control and Overseas Entities registers, and planning and tax implications specific to the deal.
Maritime Capital's own track record reflects the same pattern of diversification: self-storage and leisure conversions such as Storage Box in Hersham, branded hospitality including The Forbury Hotel in Reading and Raithwaite Sandsend in Yorkshire, and retail assets alongside the more familiar office and residential holdings. The common thread isn't the sector – it's a covenant and a business model resilient enough to justify the allocation in the first place.
Few asset classes hold up as well across multiple generations as real estate. A well-managed property can be improved, repositioned and passed down without a fixed exit forced by a fund's term, which matters to families thinking in decades rather than years. That said, realising the benefit depends on active management – a passively held property doesn't generate the same value as one where lease strategy, service charge control and repositioning decisions are being made deliberately.
Hungerford Park shows what that looks like over a genuinely long horizon. Acquired in 2005 as a 300-acre estate, it's been built over two decades into a working farm, a holiday-let business and an events venue – the kind of layered, multi-generational value creation that a fund's fixed term could never accommodate, and that only comes from treating the asset as a long-term project rather than a static holding.
Most family offices don't carry deep in-house real estate expertise alongside their wider investment team, which is why property is often the asset class most commonly brought in through a specialist partner rather than managed entirely in-house. Maritime Capital works alongside family offices and their existing advisers – wealth managers, investment managers and private banks – on the UK commercial property portion of the portfolio specifically, from acquisition through to ongoing asset and property management.
We acquired an office building on Old Queen Street in Westminster for £2.2 million. Close to St James’s Park, the property had an exceptional location but was underused in its existing form.
We saw the opportunity to reposition it entirely, creating a residential scheme that would stand out in London’s emerging luxury market.
Over the course of a four-year project, we invested £4.5 million in a comprehensive conversion.
This involved adding a new top floor with curved glass doors overlooking the garden, as well as reconfiguring the interiors to create flowing, liveable spaces.
Every element was carefully considered, from bespoke lighting designed by Sally Storey, to furniture supplied by William Yeoward, and gardens curated by Terra Firma Landscapes.
Conservation architects Donald Insall Associates led the design, ensuring that the building’s period character was preserved while introducing modern touches.
The scheme was also notable for its innovative details. We installed dumb waiters linking the kitchen to the dining areas, maximising convenience and efficiency. The new interiors blended practicality with sophistication, and the house was finished to a standard that few properties in Westminster could match at the time.
Before the eventual sale, the property was rented to a high-profile musician, with Savills describing it as “the best house in London to let.”
The project was successfully concluded with a sale price just under £9 million.
Old Queen Street ably demonstrates how we bring together vision, market awareness and execution.
It highlighted our ability to anticipate demand in the ultra-prime London residential market at an early stage, while working within complex planning and design frameworks.
And most importantly, it showed how an under-utilised office building could be reimagined by us as a one-of-a-kind home, delivering both strong returns and a distinctive addition to the city’s housing stock.
(Image credit: Beauchamp Estates)