It does keep hot drinks hot for 12 hours, but it’s on summer adventures that this flask really comes into its own, keeping iced drinks cold for more than 24 hours. Insulated cup: Good flasks also pay attention to the insulation of the detachable cup, if they have one.

It comes in a wide range of colours, ranging from pastel matte options to fun gradient styles, making it a perfect camping or travel accessory for the style-conscious among us. Once sealed, it can keep food hot for up to six hours, while boiling water will stay piping for ten or more.

Finally, there’s an additional loop handle on top so it can easily be attached to bags or simply carried this way. Flasks come in a huge range of shapes, sizes and openings, and with varying claims as to how long they'll keep drinks hot or cold. We also filled the flasks or cups with boiled water and then used that water to make a cup of tea for our 'tea test', and scored it out of ten based on how hot the resulting drink was.

It’s an excellent feature on the 1000ml flask, which although feels a bit top heavy, is lightweight overall and also comes with the option of an adjustable shoulder strap.

The 100% stainless steel construction of today’s flasks means there’s no risk of inner walls shattering when dropped. Multi-wall insulation: Double-wall insulation creates a vacuumed layer, which is vital for keeping hot drinks hot and cold drinks cold. Would you prefer one that’s tall and thin, or will that end up poking out of the top of your pocket?