to abandon or betray someone in order to protect or advance one’s own interests—originally (British politics, 1971) ‘to push someone under a bus’—derived from ‘to walk under a bus’ (British politics, 1966)
to be glad of minor benefits, especially in an otherwise unpleasant or troublesome situation—first recorded in The Heart of Midlothian (1818), by Walter Scott
a bias whereby people who have little ability in, or knowledge of, a particular task or subject tend to overestimate their capabilities—USA, 2008—refers to David Dunning and Justin Kruger, who described this bias in the Journal of Personality and Social Psychology in 1999
a difficult, uncooperative or unsociable person—UK, 1829—from French ‘mauvais coucheur’, literally ‘bad bedfellow’, with original allusion to a person whom a traveller had to share a bed with when stopping over at an inn
an event or occasion at which the expected principal participant is not present—coined after ‘Hamlet without the Prince’—‘Lear without the King’ 1904—‘Henry V without the King’ 1964
UK, 1999—refers to ‘Waiting for Godot’, a play by Samuel Beckett—absurd phrase, since the titular character never appears in the play—always occurs in association with the phrase ‘Hamlet without the Prince’
(literally) to sit at a table; (figuratively) to establish oneself firmly in a situation—‘to put one’s feet under the same table with somebody’: (literally) to sit at a table with somebody; (figuratively) to associate oneself with somebody
every contribution towards a goal is valuable, regardless of how small it may be—UK, 1707—in Britain, particularly associated with Tesco, which has used this phrase as its slogan since 1993
various meanings, in particular: something with a larger capacity than its outward appearance suggests—UK, 1968—the name, in TV series Doctor Who, of a time machine outwardly resembling a police telephone box, yet inwardly much larger