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Fractional CTO London — Jamie Buchanan

Jamie Buchanan — fractional CTO serving scaling companies in London and across the UK. Senior technical leadership, two to three days a week, with the operating experience to make decisions that will still be defensible in three years.

Embedded with your executive team. Accountable for outcomes. London-based in-person or remote.

The Vanarama story

Jamie spent seven years building Vanarama from a £20m business to a £200m AutoTrader acquisition — as CTO and a member of the executive board, responsible for technology, product, and Director-level analytics across an FCA-regulated vehicle leasing marketplace.

The team scaled from a single in-house technologist to over thirty people across engineering, product, QA, data, and infrastructure. The platform operated under SMCR governance, served both B2C and B2B customers at scale, and required the credit risk, pricing, and analytics capability of a regulated financial services business. Jamie led the technical and analytical workstreams for two VC funding rounds and the final strategic acquisition.

The patterns on this page are not theoretical. They are decisions made, mistakes paid for, and organisations built inside a real operating business through every stage of its curve. Read Jamie's full bio or see the Vanarama case study.

When a fractional CTO makes sense

London is full of companies in the stage where technology decisions start to feel genuinely dangerous — not because the team lacks skill, but because nobody in the room has the experience to know which decisions will age well and which will become expensive mistakes eighteen months later. These are the scenarios we see most often. More detail is in our guide to hiring a fractional CTO.

Pre-Series A technical validation

Raising a round and need credible technical leadership named on the cap table story. A fractional CTO with operating experience reassures London VCs during technical due diligence and gives the founding team a named CTO without the full-time burn.

Post-PMF scaling through the messy middle

Your engineering team has grown from two to eight or twelve people. Features ship, but nobody owns the architecture. Accidental architecture is starting to compound. A fractional CTO brings the strategic perspective before debt becomes expensive.

Legacy platform decisions

A migration, replatform, or major architecture call is coming — one you cannot afford to get wrong. The existing team is too close to evaluate independently, and the vendors you are talking to have a commercial stake in the answer.

CTO-less executive team

Board and investors are asking questions about technology that nobody internal can answer credibly. You are not yet ready for a full-time CTO, but going another quarter without a technical voice at the exec table is becoming untenable.

What you actually get

A fractional CTO is accountable for outcomes, not opinions. The distinction matters. A consultant leaves with a document; a fractional CTO stays long enough to see decisions play out, adjust course when reality diverges, and build the internal capability the team needs to eventually operate without them.

  • —Weekly strategic architecture calls with founders and leadership
  • —Executive-team presence at leadership meetings and off-sites
  • —Hiring support — role design, interviews, candidate evaluation
  • —Investor and acquirer technical due diligence preparation
  • —Build-versus-buy judgement calls on every meaningful decision
  • —Independent vendor and agency management
  • —Board-level technical reporting and governance frameworks
  • —Mentorship for your senior engineers and tech leads

Engagement model

Typical engagements are two to three days per week, minimum three to six months. London on-site presence at least once a week where it is useful — informal conversation and observation are where technical leadership lives, and most of that does not happen on video calls. Remote the rest of the time.

Direct reporting line to the CEO or founder. Burying a fractional CTO under a non-technical manager defeats the purpose of the role. If your board or investors want direct access, that works too — part of the remit is translating technical reality into business terms that non-technical stakeholders can act on.

Scoping happens through a 30-minute intro call. No procurement hoops, no discovery-phase invoice, no RFP. We discuss where your business is, where you need to be, and whether fractional leadership is the constraint worth solving. London-based companies get in-person where useful; UK-wide clients get regular travel built into the engagement rather than treating it as purely remote.

Also serving UK-wide — see our general Fractional CTO page for the UK-wide overview, or read the deep-dive guide to hiring a fractional CTO for the full framework.

Frequently asked questions

What is a fractional CTO? +
A fractional CTO is a senior technical leader who embeds with your team for a defined portion of each week — typically two to three days — and takes ownership of technical outcomes. The role sits between a consultant who writes a report and leaves, and a full-time CTO you cannot yet justify. The distinction is accountability. A fractional CTO stays long enough to see decisions play out, adjust course when reality diverges from plan, and build the internal capability your team needs to eventually operate without them.
How is this different from hiring a full-time CTO? +
A full-time CTO owns every technical decision, every day, and usually makes sense once your engineering team exceeds fifteen to twenty people or you are operating under significant regulatory complexity. A fractional CTO works two to three days a week and is the right fit for founders in the stage between needing senior technical thinking and being ready to absorb a full-time executive. Many fractional CTO engagements end with the fractional CTO helping define the role, recruit the replacement, and hand over — so the arrangement is genuinely temporary by design.
Do you only work with London companies? +
No. Jamie is London-based and most engagements are with London startups and scaleups, but the work regularly extends to the South East and remotely across the UK. On-site presence matters for the first few weeks of any engagement — informal conversation and observation are where technical leadership lives — so geography shapes how an engagement is structured. For London clients, in-person at your office is the default. For UK clients outside easy London reach, regular travel is built into the engagement rather than treating it as purely remote.
What is the typical engagement length? +
Minimum three to six months. Anything shorter is consulting, not fractional leadership. Three months is the floor for building relationships, auditing the landscape, and beginning meaningful change. Six months is more realistic where the technical challenges run deeper — legacy modernisation, platform decisions, or hiring a senior engineering leader. Most engagements extend beyond the initial term because the work reveals itself as it progresses.
Do you help with CTO recruitment after the fractional engagement ends? +
Yes — and this is often the planned endpoint. A fractional CTO is well-placed to define the full-time role, design the interview process, evaluate candidates with the technical depth the business now requires, and hand over cleanly. The best engagements end with a fractional CTO staying on in a lighter advisory capacity for one to two months after the full-time hire starts, to support the transition without getting in the way.
Can you join board meetings and investor presentations? +
Yes. Technical due diligence, investor presentations, board-level technology updates, and audit responses are part of the scope. Having a named CTO with credible operating experience — seven years scaling Vanarama from £20m to £200m, two VC rounds, an FCA-regulated trading environment, and an acquisition by AutoTrader — reassures investors and acquirers in a way that a consultant's report cannot.
How do we scope an engagement? +
A 30-minute intro call — no procurement hoops, no discovery-phase invoice. We discuss where your business is, where you need to be, and whether fractional leadership is the constraint worth solving. If it is, we agree scope, time commitment, and start date in a follow-up conversation. If it is not, we will say so and point you at a better fit. The starting point is always the problem, not the proposal.

Ready for the right technical conversation?

Tell Jamie where you are, where you are trying to get to, and he will tell you honestly whether fractional leadership is the constraint worth solving. 30 minutes. London-based or remote.

Book a 30-minute intro call