An insulated jacket is one of the most useful items in a hiking pack. It keeps you warm during breaks, delays and cold descents. The big choice is down or synthetic insulation.

Down is warmer for its weight. It packs small, feels comfortable and is excellent in cold dry conditions. If you want maximum warmth with minimum bulk, down is hard to beat.

The weakness is moisture. Down loses performance when it gets wet. Modern water-resistant down helps, but it still needs care. In the UK, where rain and damp air are common, this matters.

Synthetic insulation is heavier and bulkier for the same warmth, but it handles moisture better. It still insulates when damp and dries faster than down. This makes it a sensible choice for wet UK hiking, winter day walks and stop-start conditions.

For backpacking, down is attractive because it saves space and weight. Keep it protected in a dry bag and only use it when you are stopped or in camp. Do not wear it as your main layer while sweating uphill.

For day hiking in wet weather, synthetic can be more forgiving. If it gets a bit damp from rain or condensation, it is less of a problem.

Fit matters with both. The jacket should fit over your base and mid layer but still sit under a waterproof shell if needed. A hood adds warmth and is worth having in cold wind.

If you mostly hike in cold dry conditions, choose down. If you often hike in damp, changeable weather and want something robust, choose synthetic.

Many UK hikers eventually use both: synthetic for wet active days, down for colder camps and lightweight backpacking. But if you are buying one jacket first, synthetic is often the safer UK choice.