Case study

From Risk to Results: Delivering a Flawless Large-Scale Customer Migration

Delivering Transformation Assurance

We assured one of the UK’s largest retail banking migrations, using a risk-based, continuous approach to identify and resolve critical issues before they could impact delivery. The result: 1.2 million customers successfully migrated on time, with zero disruption, zero complaints, and no reputational impact.

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Project overview

The organisation engaged us to provide independent assurance over a high-risk, complex migration programme where failure would have had significant customer and reputational consequences. There was a need for a structured, risk-based view across the full delivery lifecycle, ensuring key risks were identified early, governance was robust, and critical areas such as testing, migration, and cutover were set up for success.

Challenges

  • Complex migration of 1.2M customers across multiple products.
  • Delivery risk across testing, migration, and cutover.
  • Fragmented testing approach across workstreams.
  • Environment constraints risking rework and delays.
  • Tight timelines with zero tolerance for disruption.
  • High regulatory and reputational sensitivity.
  • Limited visibility of cross-programme risks and dependencies.

Outcomes

  • 1.2M customers migrated successfully across multiple products.
  • 100% of milestones delivered on time.
  • Zero customer detriment or complaints uplift.
  • Zero reputational or social media impact.
  • Early risk identification prevented delays and rework.
  • Improved testing approach and programme alignment.

Challenges

  • Complex migration of 1.2M customers across multiple products.
  • Delivery risk across testing, migration, and cutover.
  • Fragmented testing approach across workstreams.
  • Environment constraints risking rework and delays.
  • Tight timelines with zero tolerance for disruption.
  • High regulatory and reputational sensitivity.
  • Limited visibility of cross-programme risks and dependencies.

Outcomes

  • 1.2M customers migrated successfully across multiple products.
  • 100% of milestones delivered on time.
  • Zero customer detriment or complaints uplift.
  • Zero reputational or social media impact.
  • Early risk identification prevented delays and rework.
  • Improved testing approach and programme alignment.

// Objectives

The main objective was to provide independent assurance across a complex banking migration, giving leadership clear visibility of risk and confidence in delivery. The focus was on strengthening critical areas and resolving issues early to support a controlled, predictable programme outcome.

// Solutions

We implemented a tailored assurance model that combined ongoing oversight with targeted deep dives into the areas of greatest risk, staying closely aligned with delivery teams throughout the programme. This allowed us to identify weaknesses early, challenge key design decisions, and support practical improvements in critical areas such as testing, migration, and cutover. By focusing effort where it mattered most, we helped stabilise delivery and maintain momentum across the programme.

// Outcomes

The programme was delivered on schedule, with all milestones met and 1.2 million customers successfully transitioned without disruption. Early intervention prevented delays and rework, while strengthening key delivery areas improved overall programme stability. The migration completed with no customer impact and no reputational issues, reinforcing confidence in both the approach and execution.

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