Short Sharp High Pitched Squeak

Hi I live in a semi-rural part of High Wycombe. Whilst sitting in my office at home I can hear a high-pitch short squeak, of short duration, and long silent intervals. I cannot figure out what it is but am absolutely fascinated by the call. I've look up and down in the bird identifier audio section, but haven't come across anything similar. I remember hearing something similar on BBC Radio 4 programme - A guide to Mountain/moorland/farmland birds. I can get you some recordings if necessary :)