However 500 to 700 is the sort of range in which the lower houses of the larger European countries tend to fall, so the UK is not out of line in its region.

One advantage of a large House is that it keeps the size of the constituencies relatively small. This is helpful for the constituent service aspect of representation. Another is that it provides a talent pool for the 100+ members of a modern British government (whether we need so large a government is another matter - the British Empire at its height had a much smaller ministry and drew more of them from the House of Lords).

In the House most backbenchers fall into two groups.

There are the hopeful sycophants, who dream of becoming an Assistant Whip or Parliamentary Under Secretary as the start of their rise to Prime Minister, who (if their party is in government) spend their time asking the Prime Minister if he will confirm how wonderful he is. A few try to attract attention by being awkward. Demonstrating talent is a high risk strategy. Certainly our present Prime Minister promotes sycophants and leaves the awkward squad to shine on the backbenches.

The other group are the older members who either begin to suspect they will not be promoted or who used to be in government and bitterly resent the idiot Prime Minister who sacked them. This latter group spends a lot of time plotting and leaking stories to journalists, in the hope the next leader will recognise true talent.

Traditionally few members of the House aspired to be ministers. They were more like the audience of a sporting event, who cheered their team and booed the opposition. Only a few members, the great orators and the men of business, aspired to have a place on the pitch. The supporters could hope for a patronage job or a peerage, but were content to take a secondary role.

Nowadays the backbenchers still function as an audience, but most of them are ambitious.

Some members can get satisfaction from committee work, but most would happily give up being a committee chairman for the most trivial junior ministerial position. A few members can be Speaker or one of the three deputy Speakers, but perhaps they should not be classified as backbenchers.

The above is of course a cynical view. No doubt many backbenchers are content to hold government to account and be respected experts on one or two topics. Others can be Bill Cash and be bores about the EU.

Any national Legislature will need one commission/group for Budget, another for foreign affairs, another for social matters, et caetera...

Actually the US federal congress, with its smaller attributions, probably needs less members than the all-powerful French or British equivalents :)

Un roi sans divertissement est un homme plein de misères