You can submit your application with all of the required supporting documents and your passport. We will take a copy of your passport and return it to you immediately. Once you have returned to the UK you can re-submit your passport to us for the visa to be affixed in the event that your application is successful.
If you are applying in person, just let the Visa team, at the counter, know that you need the passport back. If you are applying by post, include a note to the Visa team explaining why you need your passport back.
However, you are responsible for ensuring that you re-submit your passport to the office upon your return and before your proposed date of travel to Ireland.