Law students don't need any future proofing in terms of the internal spec of the laptop.
Web browsing, watching videos, word processing, video conferencing, simple spreadsheets are all totally mundane tasks for any decent laptop made in the last 10 years. So mundane that there is no actual detectable difference in speed between a 2016 premium business laptop and the most super duper of brand new laptops sold in 2025 for those tasks.
The best way to future proof a law student laptop is to have a rule of never drinking coffee near it, buying one with an aluminium or magnesium alloy case and lid, instead of plastic. Buying one with decently engineered hinges, instead of the cheapo ones put in consumer grade laptops. Never leaving it in a car overnight when it's freezing. Replacing the battery when it discharges annoyingly quickly.
£1,000 is enough to provide a law student and law professional with laptops for the next 20 years. If the right laptops are bought.
That amount of future proofing is in the price. Buy a used premium business laptop at about £200, from ebay or facebook marketplace. Replace it with another used premium business laptop at about £200 when it goes BER (Beyond Economical Repair).
A fully working HP 840 or 845 G8 for about £200 would be a sound deal. Or for something more portable, and about £20 less to buy, but with a smaller screen, a HP 830 or 835 G8 would be good.