How to Interview AI Engineers in London Without Losing Them to Your Process
A strong AI engineer should leave your interview understanding the work, the team and why they could succeed. If they leave with another vague stage to complete, your process is creating doubt.
For Seed–Series B founders hiring in London, the aim is straightforward: agree what the engineer needs to do, collect relevant evidence and make a timely decision. You can assess technical depth without turning the search into a six-week obstacle course.
Our recommendation is a focused three-stage process, with the decision-makers available before interviews begin. The speed comes from preparation, not from lowering the bar.
Define the engineering job before designing the assessment
“AI engineer” can mean someone building applications around existing models, someone developing ML systems, or someone making those systems reliable in production. One generic test will not assess all three properly.
Write down the first meaningful outcome this hire must own. Is it a customer-facing workflow, an evaluation pipeline, a retrieval problem or production reliability? Then identify the skills essential to deliver it.
The UK Government Digital and Data machine learning engineer framework, updated on 28 August 2026, includes deployment, integration and maintaining effective models alongside development. It is a useful reminder to assess the work beyond a successful experiment, although a startup’s brief will differ from a government role.
If your team is still debating the role itself, start with our guide to AI engineers, ML engineers and research scientists. Settle that question before asking candidates to prove they fit.
Tell candidates the whole process at the start
Share the stages, approximate time commitment, assessment format and expected decision date before the first substantive interview. Explain who they will meet and what each conversation is for.
In London, be specific about the workplace too. An office near King’s Cross, a team in Shoreditch and a role based in Canary Wharf create different journeys. State the actual location, required days and whether those days are fixed. “London hybrid” leaves too much unresolved.
Discuss the base salary range in pounds, equity and any sponsorship requirement early enough to avoid a preventable mismatch. Our London AI engineer salary guide covers budgeting; an interview should not become a negotiation conducted without a range.
Stage one: founder or hiring-manager alignment
Use a focused conversation to establish the mandate and mutual interest. Explain what exists today, what is still uncertain and what the engineer would own.
Ask the candidate to walk through a relevant system they helped build. What problem did it solve? Which decisions were theirs? What broke after launch, and what did they change?
Listen for specific ownership and clear reasoning. Recognisable employers, polished terminology and impressive model names are starting points for questions, not evidence on their own.
Give the candidate room to question you. They should be able to understand the runway assumptions you can share, engineering leadership, customer access and how priorities change.
Stage two: a practical technical session
Choose a small exercise that resembles the job. For an application-focused AI engineer, you might provide a fictional support workflow with unreliable retrieval and ask how they would investigate it. For a production ML role, a deployment or monitoring scenario may reveal more.
Provide enough context to reason properly. Make it clear which tools, documentation and coding assistants are allowed. Do not surprise candidates with rules halfway through.
A useful session should expose:
- How they clarify requirements and identify missing information.
- How they diagnose a failure rather than immediately replace the system.
- How they would test quality, latency, cost and relevant security risks.
- How they explain trade-offs and decide what to do first.
Keep any take-home bounded, with an explicit time expectation. If you want a substantial project, consider paying for the time. Use fictional or sanitised material; candidates should not need to share a previous employer’s code or do unpaid production work for you.
Do not turn this into a separate research-scientist assessment unless original research is actually part of the job.
Stage three: close the remaining questions
The final discussion should resolve identified gaps and allow both sides to assess working together. It should not restart the search criteria.
If the technical evidence was strong but you need to understand stakeholder communication, explore a concrete disagreement or priority change. If the candidate is concerned about technical debt, let them speak to someone who owns it.
For US founders building a London team, protect sensible UK interview hours. Book an overlapping window and consolidate conversations rather than repeatedly asking someone to attend late-evening calls. Explain which decisions can be made locally after they join.
Use a scorecard people can actually apply
Agree a small set of criteria before the first candidate: relevant engineering depth, evaluation judgement, production ownership, communication and the ability to work within your stage of company.
Define what convincing evidence looks like for each. Interviewers should record their observations independently before the debrief. “Not sure about fit” needs a job-related explanation, not another automatic interview.
Acas guidance on interviewing recommends consistent questions where possible and preparing interviewers. It also covers asking about reasonable adjustments and planning for online connectivity problems. Build those considerations into scheduling and assessment, rather than treating them as last-minute exceptions.
Consistency should give candidates a fair opportunity to demonstrate the relevant skills. It does not require ignoring agreed adjustments.
Make decisions while the evidence is fresh
Set a debrief promptly after the final stage. Give one person responsibility for collecting feedback and communicating the outcome by the date promised.
If a genuine question remains, name it, explain why it matters and choose the smallest sensible way to resolve it. Avoid adding another founder conversation simply because nobody is ready to commit.
A suggested target is to complete the core stages within one to two weeks where calendars allow. That is a process design recommendation, not a guarantee or a London market statistic. Candidate availability and adjustments may require more time.
The takeaway for founders
Every stage should answer a defined question and give the candidate useful information. Clear scope, relevant assessment and reliable communication make a short process credible.
Dataworks helps Seed–Series B AI companies define technical hiring briefs and recruit across the UK, Europe and US. If your London search is losing momentum between interviews, talk to us about the role and the process.