Or at least, it was until recently. For while the flask's inner workings have remained unchanged for more than a century - a glass tube whose inner and outer walls are separated by a vacuum, with a silvery coating inside to reflect the heat - its outward appearance has undergone some decidedly fancy innovations of late.
Gone are the tinny tartans that delighted fishermen of yesteryear (shockingly, it is no longer possible to buy them in Britain, although they remain popular in France and Chile). In their stead are space-age steel, luminous plastics and even - perish the thought - a flask with ears (Alessi's Fred Worm, right, pounds 32; for stockists call 01920 444272).
What would Sir James Dewar, who invented the vacuum flask in 1892, make of them? The canny Scot, whose other useful invention was cordite, was more interested in liquid gases than hot coffee. It was left to a more thrusting German student of his to launch the flask commercially, which he did in 1902. Its name, Thermos - after the Greek word for "heat" - was chosen in a competition.
It was an instant success: "I consider that, for camp work in the polar region, these Thermos flasks are almost a necessity," cooed Ernest Shackleton. Today, Thermos's two English factories produce some four million flasks a year. While the original wooden cork has long been supplanted by plastic, the cup of a lid is a perennial favourite (Habitat have a pounds 5 flask with cup; for stockists call 01645 334433).
For followers of fashion, there is a new rash of possibilities. An American post-modern architect, Michael Graves, has created Alessi's Euclid, left, a ball of a flask with cube feet, in fetching colour combinations (pounds 52 from InHouse in Glasgow, 0141-552 5902, and Edinburgh, 0131 225 2888), while Ross Lovegrove and Julian Brown's Alfi vacuum jugs employ PMMA - the stuff car lights are made from (in various colours, pounds 35.95 at Aero, 0171-221 1950).
Toughest and sleekest is the baton-like metal tube: Zojimushi's Tuff Slim flask (from Heal's, 0171-636 1666); Thermos's own (pounds 30 at Aero, 0171- 221 1950); Marks and Spencer's Slimline (pounds 25, call 0171-935 4422 for stockists; 0345 905905 for a catalogue); while David Mellor's Butterfly elite even comes with a strap (pounds 29.10; pounds 21.55 without; 0171-730 4259).
And for those who can't do without colour, Bodum's Lipstick flasks, far left, come in blue, yellow, red and green (pounds 9.95 from The Conran Shop, 0171- 589 7401). What a picnic.Reuse content