CAS Shield
An AI-powered mock interview system that gets students ready for UK visa credibility interviews.
Built for the company's internal platform, so implementation details stay private. This page covers what it does and why it was built the way it was.
The problem
Before a UK university issues a CAS (Confirmation of Acceptance for Studies), it has to be satisfied that the student is genuine, and UK Visas and Immigration can interview any student before granting a visa. A student who can't explain in their own words why they chose the course, how their fees are paid, or what they plan to do afterwards is a red flag, however strong their paper application looks.
Interview readiness used to be checked informally: a phone call, a checklist, or nothing. That was inconsistent, because two students with the same weak points could be treated differently, and it left no record of the due diligence that had been done.
How it works
- 1
Set up
A compliance officer creates an interview for a student's application. Questions come from a vetted question bank and are personalised with the student's own details, such as university, course and fees.
- 2
Interview
The student takes it online like a real credibility interview: a device check, preparation time for each question, then a timed, recorded answer.
- 3
Analysis
Each answer is transcribed and assessed by AI against clear criteria: is it specific, accurate and clear? Answers are also checked against each other, so contradictions across the session are caught.
- 4
Human review
A compliance officer watches each recording next to the AI's findings, edits the feedback where needed, and approves every question.
- 5
Report
The student receives a clear report with strengths, weaknesses and a coaching tip for each question.
Key decisions, and why
A human always has the final say
AI is fast and good at spotting contradictions in a long transcript, but it can miss context, like a nervous but well-prepared student. Nothing reaches a student until an officer has reviewed it.
A vetted question bank, not free-form AI questions
Question wording and grading criteria are compliance-sensitive, so they are version-controlled and reviewed like code. The AI only selects and personalises questions; it never invents them.
Consistency across answers, not just single answers
The real red flag is a story that doesn't hold together, like a funding source that changes between answers. Some questions are graded on their own; others are cross-checked against the whole session.
No silent overrides
Officers can reword the feedback but can't flip the underlying verdict without changing the evidence. That keeps every judgement honest and explainable.
Everything is auditable
Who created the interview, who wrote the questions, who reviewed each answer and who approved the report are all recorded. If a case is ever challenged, the due diligence is on file.
Impact
- Replaced an informal, inconsistent readiness check with a structured, repeatable and auditable process.
- Became a key differentiator for the firm.
- Measurably improved students' visa interview success rates.
My role
- Identified the problem and proposed the solution.
- Led design and development end to end, from the question bank and grading rules to the student and officer experiences.
- Wrote a complete technical and functional reference so other engineers and operations staff can maintain and use it.