Principle
Keep priority pressure separate from feasibility evidence
Importance can buy resources or scope changes; it cannot repeal dependencies.
When it fits
- A high-priority request is assumed to require less time.
When to avoid it
- Throwing more people at tightly coupled or unfamiliar work can increase coordination cost; added capacity is not automatically added throughput.
Why it matters
When priority rises, first recompute the feasible options: add capacity where work is parallelizable, remove scope, shorten approval paths, accept explicit risk or move other commitments. Do not simply shrink the estimate because the task became important.
An example
A Monday deadline is met by splitting validation and dropping a nonessential report, not by changing 'five days' to 'two' in the spreadsheet.
Check your result
Any accelerated commitment points to a concrete system change.
Keep this limit in mind
- Throwing more people at tightly coupled or unfamiliar work can increase coordination cost; added capacity is not automatically added throughput.
Connected ideas
Compare withSeparate the forecast from the commitment
Evidence and sources
Supports
The 2026 Green Book recommends explicitly accounting for optimism bias in cost, benefit and duration estimates and using historical forecast errors from similar proposals where available.
The guidance is for UK public appraisal; the transferable principle is empirical correction, not a universal percentage uplift.
The Green Book (2026) · Optimism bias