27/04/2026
Legacy systems have always been a cost problem, but for a lot of UK SMEs they're now a compliance problem too. The Cyber Essentials MFA mandate lands today, 27 April, the Data (Use and Access) Act 2025 is already live, and PCI DSS v4.0.1 is tightening up. Meanwhile the average UK financial-services breach hit £5.74m last year (IBM 2025), and maintaining legacy typically costs 3 to 4x what the modern equivalent would.
Good news though, modernising doesn't have to mean a full rebuild.
Our new guide covers the 5 Rs framework (Retire, Retain, Rehost, Replatform, Refactor/Replace) with real UK cost bands, from around £20k up to £500k+ depending on the route. Replatforming alone tends to deliver about 80% of the benefit of a full rebuild at roughly 30% of the cost.
AI is shifting this space too. We're seeing 40 to 60% speedups on well-scoped migration work, and there's a documented case of 350,000 lines of legacy Java modernised in 4 months. That said, AI isn't taking over architecture or data-consistency decisions yet. Senior engineer review is still the bottleneck that keeps the work sensible.
If modernisation is on the table for you this year, worth reading before you commit to a route.
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