Illustrative cost

£7,500 to £22,000 ex VAT

Typical: £13,000
Duration: About 5 weeks
Effort: 15 to 30.5 days

Illustrative estimate, not a quote. Real prices vary.

Worked out from UK freelance contractor day rates in job adverts, with no consultancy or agency margin added. Consultancies and agencies usually charge more.

Source: IT Jobs Watch. Rates read on 15 November 2026; costs computed on 15 November 2026.

What is included

Threat modelling of the AI applications in scope
Hands-on adversarial testing
Review of guardrails, logging and access
A risk-rated report and retest

Deliverables

Threat model
Findings report with risk ratings
Retest letter

Assumptions

Up to two applications in scope
A test environment the testers may attack
Written authorisation before testing

Not included

Infrastructure penetration testing
Fixing the issues found

Project plan

Phases run one after another, about 5 weeks in all.

Phases, their length and main tasks
Phase	Weeks	Main tasks
Scoping and threat model	1	Agree scope and rules; Threat model
Testing	3	Prompt injection and jailbreaks; Data leakage tests; Guardrail review
Report and retest	1	Report; Retest fixes

Who does the work

Person-days per role in each phase, low and high effort.

Days by phase and role
Phase	Role	Days (low to high)
Scoping and threat model	Cyber security consultant	2 to 3.5 days
Testing	Cyber security consultant	7 to 12.5 days
Testing	Generative AI (LLM) engineer	2 to 5.5 days
Report and retest	Cyber security consultant	2 to 5.5 days
Report and retest	Generative AI (LLM) engineer	2 to 3.5 days

How the cost adds up

Cost by role: low, typical and high, before rounding
Role	Low (days × 25th percentile)	Typical (days × median)	High (days × 90th percentile)
Cyber security consultant	11 × £520 = £5,720	16.25 × £581 = £9,442	21.5 × £675 = £14,514
Generative AI (LLM) engineer	4 × £417 = £1,668	6.5 × £543 = £3,529	9 × £825 = £7,426
Total, rounded	£7,500	£13,000	£22,000

How these estimates are worked out

Effort: for each phase we estimate how many days each role works, as a low and a high case. These are our estimates for a typical project of this kind, not measured data.

Rates: each role's daily rate comes from UK contract job adverts over the last six months, as published by IT Jobs Watch. These are freelance contractor rates as advertised, not what was paid, and not what a consultancy or agency charges.

Low end: the low-effort days at each role's 25th-percentile rate. We use the 25th percentile, not the 10th, because the lowest effort at the cheapest rates gives a floor few buyers would ever meet.

Typical: the mid-point between low and high effort, at each role's median rate.

High end: the high-effort days at each role's 90th-percentile rate.

Totals are rounded to the nearest £500 below £10,000 and the nearest £1,000 above, and exclude VAT. Phases run one after another.

Not included:

Software licences, model and hosting fees
Travel and expenses
Your own staff's time
A consultancy's or agency's margin, overheads and risk

Real prices vary with the supplier, the state of your data and systems, how much of the work your own team does, where the work happens and how much risk the supplier carries. Consultancies and agencies usually charge more than these contractor rates, and a fixed price usually costs more than time and materials because the supplier takes the risk.

Sources

Source: IT Jobs Watch: UK contract job adverts quoting a daily rate, 6 months to 15 November 2026. Each role's page was read on 15 November 2026. Published under CC BY-NC-SA 4.0.

Day rate sources, one row per role, read on 15 November 2026
Role	IT Jobs Watch page	Rates quoted	25th percentile	Median	90th percentile
Cyber security consultant	Cybersecurity Consultant	86	£520	£581	£675
Generative AI (LLM) engineerIT Jobs Watch has no "LLM Engineer" or "Prompt Engineer" title with daily rates; mapped to the closest title, Gen AI Engineer.	Gen AI Engineer	30	£417	£543	£825

AI and LLM security review for a mid-sized fintech