The Marylebone-based outfit, which has nine offices across the UK, reported income of £12.4 million for the year to the end of September 2025 in its latest full-year accounts.
This was up from £10.9 million in the prior period, the ‘significant’ growth attributed to a range of new and repeat business.
Last month, Donald Insall Associates scooped the coveted crown of Practice of the Year, selected from a strong list of AJ100 Champions, which featured Foster + Partners, Orms, Populous and Sheppard Robson.
But while the practice’s turnover was up, its pre-tax profit fell, from £312,000 in the 12 months to September 2024 to £191,000 in the latest period.
Operating profit also slumped, by 63 per cent to £107,000 in the most recent spell, although the company said this reflected an improvement in underlying trading performance after adjusting for exceptional items. It received a one-off payment from an insurance claim in the previous period.
The practice’s administrative costs soared by almost a fifth to £4.7 million last year as it continued to invest in systems and processes, which it said contributed to the boost in income.
The practice, which achieved B Corp status in July 2024, had £3.5 million in the bank at the end of last September, up from £2.7 million a year earlier.
Its UK turnover increased from £10.9 million to £12.1 million in the latest period, while it made £116,000 from Europe and almost £200,000 from the rest of the world. It didn’t have any non-UK income in the prior year.
Donald Insall’s average monthly headcount fell by one person to 140 in its most recent period. Nonetheless, overall staff costs grew by a tenth to £8.2 million.
Its decade-long conservation of Parliament’s 11th-century Westminster Hall received the Michael Middleton Special Award and the AABC Conservation Award at the 2025 Civic Trust Awards.
Directors described the year’s performance as ‘satisfactory’, adding: ‘We were pleased to continue our strong relationship with existing clients and secure exciting new clients and significant projects across our studios.
‘The company continues to explore growth opportunities both in the UK and overseas, and continues to manage carefully its organic growth to ensure stability for all stakeholders.’
AJ100 Practice of the Year judges said of Donald Insall: ‘They are clear on their identity and it feels tangible and of the time. They are not paralysed by the heritage piece. They are really good architects.’