Thermos Originals Premier 34
Price: £8.47 Retained temp (deg C): 82
The lining is old-tech glass as opposed to steel, but the Premier gives little away to more modern designs. Its heat-retaining ability was beaten only by the Rock from the same maker - impressive stuff considering the Premier is much cheaper - while it's bigger than its Thermos brother, too. Features include a twist-and-pour stopper, lid storage and two same-size mugs with generous handles. Due to its fragile lining, this one can't be handled as roughly as more robust flasks. But the performance and price earn it our Best Buy award.
