Service
You don't have a CTO-sized workload. You have CTO-sized decisions.
Ten or so a quarter, and each one is expensive to get wrong. Architecture you will live with for years. Build or buy. The first senior hires. What to actually do about AI, and what to leave alone. Hiring someone full-time to make ten decisions is the most common mistake we see after a raise, and it takes two quarters to arrive.
The alternative is reserved senior capacity: a set number of days each month, held for you, from someone who has sat in the chair. Sometimes called a fractional CTO. Structured so you are buying attention rather than a job description.
The Retainer Family
Same terms across the family. Pick the level of commitment that matches the shape of the engagement. Move up or down when the shape changes.
Advisory
£1,500/month
Founders and small teams who want occasional access to senior judgment.
Standard
£4,500/month
Meaningful continuity for mid-stage companies with decisions in flight.
Embedded
£7,500/month
A named CTO outcome across the business. Top of the family.
We hold a small number of retainer slots, so each client gets senior attention, not a junior with an escalation path. At most two clients fit at Standard or Embedded, and existing clients get first refusal on renewal. The cap is what keeps the attention senior.
What the cap buys you
Every term below exists to protect the same thing: that the time you reserve is senior, and that it is yours.
Two clients at Standard, or one at Embedded. Not both
You get the partner's attention, not a junior with an escalation path. The cap is the product, not a limitation of it.
Your days are reserved for the month
Held for you and not sold twice, so another client's emergency is not your problem.
The agenda is set together at the start of each month
You decide what the time is spent on, against the decisions actually in front of you.
Move between levels, or leave, on a month's notice
Nothing locks you in. If the shape of the work changes, the commitment changes with it.
Two things it is not
Not incident cover
This is scheduled senior attention, not a pager. Running systems live under a separate support agreement, which is how you buy cover someone is resourced to give.
Not a way to buy delivery
Date-bound work runs as fixed-scope delivery against a signed done-test, where the risk sits with us and the price is fixed. Pulling it into a retainer would cost you more and guarantee less.
If what you need is something built to a date, fixed-scope delivery against a signed done-test is the better product and we will say so. Retainer clients get priority in the delivery queue.
When a retainer is the wrong answer
Reserved capacity earns its keep when there is something to steer: a product in flight, a build under way, decisions with money behind them. If that is still a few months off, a fixed-scope build or a standalone assessment is the better first engagement, and we will say so on the call rather than take the retainer and hope. We would rather have the right engagement later than the wrong one now.
How a month runs
We agree the agenda at the start of each month and schedule the reserved days against the work. Active engagements get a weekly written update; everyone gets a quarterly scorecard.
Month opens: agenda set together
Review top risks, progress on open items, and upcoming decisions. Agree the priorities for the month.
Days scheduled at our discretion against the agenda
Architecture decisions, board-deck prep, vendor evaluations, security review, strategic planning. Whatever the agenda carries.
Weekly written update, quarterly scorecard
Active engagements get a one-page Friday report. Every quarter, a board-ready scorecard covering the metrics that matter most.
Advisory Topics
Your retainer adapts to whatever matters most. Each topic could be a single session or an ongoing focus across multiple months.
Strategy & Planning
- Technology roadmap and 90-day delivery plans
- AI strategy: what's real, what's hype, where to start
- Architecture review, scalability, and technical debt
- Cloud strategy and migration planning
- Build vs. buy decisions with the trade-offs stated plainly
Security & Compliance
- Cybersecurity posture review and risk assessment
- Cyber Essentials, ISO 27001, and GDPR alignment
- Incident response planning and crisis preparation
- Supplier and vendor security assessment
People & Operations
- Technical hiring strategy, job specs, and interview support
- Engineering team structure and productivity metrics
- Vendor and supplier evaluation: independent, no kickbacks
- Support operations, SLAs, and operational improvement
Board & Governance
- Board-ready technology and cyber risk reporting
- Budget development, cloud cost optimisation, and spend governance
- Data architecture, governance, and quality assessment
- Due diligence preparation ahead of fundraise or sale
The Quarterly Scorecard
Every quarter, retainer clients receive a board-ready scorecard covering the metrics that matter most to their business. We select the areas together. Common examples include:
Who This Is For
Startups & Scale-ups
Companies with a build programme in flight that need senior technology leadership but aren't ready for a full-time CTO hire.
Non-Technical Founders
CEOs and founders who need a trusted technical advisor to help make confident technology decisions.
Boards & Investors
Organisations that need independent technology oversight and board-level reporting on technology and cyber risk.
CTOs Who Value a Sounding Board
The best leaders still use a coach. An experienced second opinion on strategy, architecture, and stakeholder management, someone to pressure-test decisions with, not report to.
Why Mangrove
- 20+ years as CIO and CTO: we've sat in the chair, from startups to enterprise, across financial services, cybersecurity, and beyond
- Security built in: 20+ years in cybersecurity. CISSP, CISO at Earthport, responsible for security at Spark. Security leadership comes standard, not as an add-on
- AI-literate: we can assess AI opportunities and vendor claims properly, not just parrot the hype
- Scarcity is structural: capacity is deliberately capped, so a retainer buys the partner's attention, not a slice of a delivery team
What are the next three decisions you have to get right?
Bring them to a 30-minute call. You'll leave with a straight view on each one, whether or not anything follows, and a straight answer on whether a retainer is even the right shape for you.