In the year to mid-2024 (the most recent period with detailed full breakdown):
The population grew by over 755,000 people — the second-largest annual numerical increase in more than 75 years.
This took the total from ~68.5 million (mid-2023) to ~69.3 million (mid-2024).
Net international migration (people arriving minus those leaving) was the dominant driver, accounting for 98% of the growth at around 739,000 people (with ~1.24 million immigrating and ~497,000 emigrating).
Natural change added only a tiny fraction (~16,000), as there were slightly more births (~662,000) than deaths (~646,000) — but birth numbers were at their lowest in at least 42 years.
By the year to mid-2025, net migration fell sharply to 204,000 (with ~898,000 immigrating and ~693,000 emigrating), reflecting recent policy changes that reduced inflows (especially non-EU work and study visas) and increased outflows. Even so, migration remains the main reason the population continues to grow at all, since natural change is now close to zero or slightly negative in some projections.