Legacy IT systems – decades-old platforms, patched and propped up over time – have been responsible for consuming nearly half of the UK government’s IT budget in recent years, while simultaneously creating significant operational risk. Analysis from the Organising for Digital Delivery report revealed that by 2019, £2.3bn of the £4.7bn IT budget was devoted to “keeping the lights on”. The financial exposure over the next five years was estimated at between £13bn-£22bn. It is, according to the government’s own assessment, unsustainable.
A more recent review for the policy paper A Blueprint for Modern Digital Government confirmed that the problem is worsening. Over 100 organisations – including local authorities, NHS trusts, police forces and central government departments – participated in the study, and the findings were stark: despite previous investments in remediation, the number of high-risk legacy systems rose by 26 per cent from 2023 to 2024. Public sector organisations are struggling to modernise while maintaining operations, and are often reliant on unsupported technology.
Technical and infrastructure constraints
The technical challenges are profound. Large volumes of operational data remain trapped in systems lacking standard interfaces and reliant on proprietary formats. Computational capacity is often insufficient to support modern workloads, particularly those using artificial intelligence, while legacy architectures impose structural constraints that slow or restrict deployment of new capabilities at the pace required for the information age. Complex licensing arrangements add further rigidity. Frequent legislative changes can force departments to extend existing systems rather than replace them, particularly when reforms coincide with ongoing modernisation, creating further technical debt and opaque dependencies.
Organisational culture and mindset
Culture presents another barrier. In many public sector organisations, IT is still seen primarily as a cost rather than a transformation enabler, fostering siloed working practices and protective behaviours that can stifle innovation. Risk aversion is evident across many areas of public sector, with caution often prioritised over experimentation.
Yet those organisations adopting a product-centric mindset show progress. By continuously evolving systems, planning for retirement alongside delivery, and monitoring supplier and sector trends, they reduce the risk of systems becoming legacy. This approach encourages proactive stewardship and a longer-term view of digital service delivery.
Resource allocation and talent shortages
Resource constraints exacerbate the challenge. Significant portions of IT budgets are consumed by legacy maintenance, leaving limited funds for the public sector to innovate and modernise, and costs rise when new systems run in parallel with old ones. Talent shortages further complicate the picture: recruiting and retaining specialists to manage legacy and modern platforms is increasingly difficult. Many subject matter experts are approaching retirement, and the pool of new entrants with these skills is small. Without structured knowledge transfer, dependencies remain undocumented, increasing risk. According to the State of Digital Government Review, cyclical funding – periods of heavy investment followed by minimal maintenance – also contributes to technical debt and hinders the long-term planning that is required to achieve transformation at scale.
Data governance and quality challenges
Data quality and governance amplify risk. Legacy systems often lack clear documentation of business rules, making it difficult to replicate functionality or verify outcomes. Poor data quality undermines AI performance, while inconsistent governance complicates compliance with modern security and privacy standards, increasing operational risk during migration.
A modernisation framework
A holistic, multi-layered approach is essential. Legacy remediation should be treated as a transformation programme rather than a purely technical upgrade. Strong governance, clear accountability and a product-based delivery model support continuous iteration and proactive system retirement.
Operationally, standardising processes and adopting platform-based solutions reduce duplication and enhance scalability. Comprehensive documentation and structured knowledge transfer are crucial given the ageing workforce. Metrics and regular reviews maintain accountability and sustain executive attention.
Resource strategies must secure long-term investment, strengthen internal capability and create attractive career paths. Partnerships with external experts can address capacity gaps, but internal teams must acquire the skills necessary to manage modern systems sustainably. Investment must recognise that digital infrastructure requires ongoing support rather than one-off expenditure.
Risk management should underpin the programme. Standardised approaches to legislative changes, continuous monitoring of system performance, and thorough documentation of business rules and dependencies reduce uncertainty and operational risk.
Success factors
Successful modernisation hinges on leadership, culture, resources and governance. Strong executive commitment is vital, including clear vision, prioritisation of legacy remediation and sustained attention. Cultural change – shifting to a product-based mindset – encourages innovation, collaboration and pride in modernisation achievements. Sustainable resource strategies, including long-term funding, talent development and knowledge management, are essential to avoid recurring technical debt. Effective governance ensures accountability, monitoring and stakeholder engagement, enabling programmes to continue despite leadership changes or shifting priorities.
Several public sector organisations demonstrate the benefits of modernisation. The Royal Borough of Kingston and the London Borough of Sutton are examples of two London boroughs saving money through the use of AWS services. Digital transformation in local government comes with unique challenges, especially when managing shared IT services across multiple organisations; the two boroughs migrated from on-premises data centres to AWS cloud infrastructure. Through strategic collaboration with AWS, the councils were able to navigate these challenges and achieve a successful cloud transition. Similarly, NHS Midlands and Lancashire launched a scalable, cost-effective patient contact platform on AWS, working together with AWS Partner Digital Space. The solution reduced patient waiting lists by 9-14 per cent. The University of Sheffield improved performance 15-times by working with Perform Partners in migrating to AWS with a goal of gaining a more modern, faster-performing system for managing student needs.
The Ministry of Justice’s analytical platform is built using AWS and is used by over 500 data and analytics professionals. This has enabled the ministry to develop critical insights based on advanced analytics, machine learning and risk-assessment tools. AWS and the Ministry of Justice are now working in partnership to improve operations using AI and machine learning, driving innovation while maintaining cost efficiency with public funds.
The forward path
Organisations should adopt a holistic strategy encompassing technical, organisational and cultural dimensions. Clear vision, consistent processes, robust accountability and investment in digital skills are central. Emerging technologies, including AI, can play a supportive role, provided data quality and security remain priorities.
Structured delivery frameworks – discovery, envisioning, needs assessment, mobilisation and scaling – help maintain momentum. Discovery workshops can map risks, clarify dependencies and identify remediation priorities. Success depends on balancing incremental progress with long-term transformation, ensuring modernisation is sustainable, measurable and aligned with organisational objectives.
To support ongoing collaboration around legacy challenges in the public sector, we have compiled insights and practical approaches from across government in our AWS Legacy Exit Solutions Guide. Every organisation’s modernisation journey is different, and to help explore the right path, we offer facilitated workshops that delve deeper into these strategies and their application.
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