FIRE on £5,000/month — maximum velocity.

£5,000 per month — £60,000 a year — is extraordinary. This requires a very high income (£100,000+, often £150,000+ for single earners) or a high-earning dual-income household. With 7% returns and £25,000 annual expenses, your £625,000 FIRE number is reachable in roughly 7-8 years from zero. Start at 30, financially independent by 37 or 38. At this savings rate you're saving 2.4 times your annual retirement expenses every year — investment returns are almost irrelevant to the timeline. The binding constraints are tax wrappers: the pension annual allowance (£60,000) and ISA (£20,000) together only absorb £80,000, meaning significant sums must go into taxable accounts. For earners above £100,000 adjusted net income, the personal allowance taper creates a 60% effective marginal tax rate, making pension salary sacrifice exceptionally valuable. At £5,000/month, the real question shifts from 'can I retire early?' to 'what will I do with my time?' — which is arguably the harder question.