Ominous by its absence the missing seat suggests some sort of catastrophic intervention, a result of intent or design. As a design fault of course eventually the structural weak plastic will give way under routine subjegation to the rigours of the average British physique a result of the environment these objects are destined for.
The chair has come to symbolise the individual. The use of a chair as a weapon of the discontented is poingant not just barbaric.
As an object of destructive intent the chair has its place in the volatile history throughout British history from props in hangings to missiles in the stadiums across the country (to be replicated abroad, who can forget scenes of British hooligans lobbings chairs at startled and bemused hosts in numerous competitions)