Ground movement callsigns (including LHR)

[myrtleman]

Hi everyone,

I was wondering if someone could explain the callsigns that are used at LHR (and maybe all airports) for craft leaving stand and taxiing to the runway for take-off.

For example, what does Bealine refer to and also why are certain airlines seemingly referred to by their registration and others by their ATC callsign? I'm quite puzzled by all of this.

Thanks,
MM