In The English Companion by Godfrey Smith, a compendium of all the things that we love best, the entry for marmalade is sandwiched between 'Marks & Spencer' and 'marques' (as in posh car brands). It does contain one misapprehension, namely that the Scots invented marmalade (they didn't). But putting that aside, his short essay on marmalade is good fun, particularly the following three points:
1: 'It does not taste right on anything but toast, and at any time but breakfast.'
2: 'To take it with butter as well is a comparatively modern function of affluence.'
An earlier post - here - agrees with this (see second extract - and, while you're at it, see AA Milne's 'The King's Breakfast' where the king is offered marmalade instead of butter), though I can't imagine it myself. The creaminess of the butter is essential as a counterpoint to the tart oranges. Still, it takes all sorts.
3. 'Marmalade still conveys the very faint sense of privilege at a price everyone can afford and remains the bittersweet debut to the English day.'
I'd never thought of marmalade as being simultaneously posh and accessible, but I think he's right.