Can the Millbrook Wool Luxury 4000 mattress really keep you cool at night? I slept on it in a heatwave to find out

Millbrook’s mattress ditches memory foam for temperature-regulating wool and breathable springs. Here’s what I loved – and what didn’t impress me

• The best mattresses: sleep better with our seven rigorously tested picks

In simpler times, everyone slept on sprung beds. A few rebels opted for futons (or even waterbeds), but back in the 20th century, most of us had mattresses with tufted surfaces and a belly full of springs that bounced when you jumped on them.

Memory foam began sneaking into our beds in the 90s, ushering in a brave new world of cushioned peace. Most of the products I’ve considered for the Filter’s best mattresses roundup contain memory foam layers to boost comfort and limit bounce. But traditional sprung beds remain unstoppably popular, and one example – the Millbrook Wool Luxury 4000 – is a bestseller at Mattress Online.