eSIM: a £200m revenue protection problem.
Tesco Mobile was preparing to launch eSIM activation — a shift away from physical SIM cards that had significant implications for customer acquisition, retention, and revenue. At the time of the project, eSIM represented a substantial and growing share of new activations across the UK market.
The risk was clear: a poor activation experience would drive customers to competitors at the exact moment they were switching. Getting this right was directly tied to protecting an estimated £200m in at-risk revenue.
I was brought in to lead the research programme that would inform the final design direction before any engineering investment was committed.
Nobody agreed on what the right experience looked like.
There were multiple competing hypotheses across the product, engineering, and commercial teams about what the eSIM activation flow should look like. Some advocated for a minimal, fast-path experience. Others pushed for a more guided, step-by-step flow. There was no shared evidence base.
The stakes made this unusually complex. eSIM activation is a technically sensitive process — errors at any point can brick a device temporarily, creating serious customer service cost and NPS damage. We couldn't afford to ship a direction and iterate.
"We needed a definitive answer, not a best guess. That meant designing a research study that could resolve genuine disagreement across senior stakeholders."
A 9-variant study. 19 participants. One clear winner.
I designed and led a large-scale moderated usability study testing 9 distinct variants of the activation flow across 19 participants. This was the most rigorous study Tesco Mobile had run for a consumer product launch.
Study design
Defined 9 variants covering different combinations of progress indicators, instruction density, error handling approaches, and device guidance. Built a testing matrix to ensure each variable was tested against a control.
Participant recruitment
Recruited 19 participants across two cohorts: existing Tesco Mobile customers considering upgrade, and prospective switchers. Age range 22–58, mixed device types (iOS and Android).
Moderated sessions
Ran 60-minute moderated sessions using realistic prototypes. Tracked task completion, time-on-task, error recovery, and emotional response at key moments.
Synthesis and recommendation
Synthesised findings into a prioritised recommendation deck presented to product leadership, commercial, and engineering. One variant emerged with clear superiority across all metrics.
Study design matrix showing the 9 variants and testing criteria
A single flow direction. Designed around the moment of doubt.
The winning variant addressed the single biggest finding from the research: users didn't abandon because of technical complexity, they abandoned because they weren't sure the process was working. The critical design principle became radical transparency at every stage of the activation.
The final recommended direction featured persistent progress visibility, proactive error prevention through device-specific instructions, and a recovery flow that preserved the user's state rather than restarting the process entirely.
I worked closely with the product and engineering teams to translate the research findings into a detailed design specification, bridging the gap between what we learned and what could be shipped.
The full prototype, variant breakdown, and final specification are available under NDA. Reach out to request access.
Research that changed the product direction.
The study delivered clear, quantified direction in a situation where the business needed certainty. The findings were adopted in full by product leadership and formed the basis of the shipped experience.
The study also had a secondary impact: it established a new standard for how Tesco Mobile approaches research-led product decisions. The methodology was adopted as a template for subsequent major feature launches.
What I learned: The most valuable research isn't always the most elegant — sometimes it's the study designed specifically to resolve a commercial decision, not just validate a design direction.