A Civil Servant in the UK is a member of the Civil Service. They tend to be the elite of the country and are drafted from Oxbridge a lot of the time (though many candidates come from the other brilliant universities in the UK. They're all good really). Often they hold very influential positions in government giving advice to the Ministers on an issue. This is why they are useful to pressure groups since they are able to directly affect decisions made.

There are many people designated as Civil Servants such as people who run the National Theatres and also National Galleries.