Set (0) form - first entry to UK

[smartchap2k]

Dear friends

Section 6.1 of SET (O) form states the following

When did you (the main applicant) first enter the UK? This refers to the
date of your first entry into the UK at the beginning of the period of stay
on which this application is based.

Question: - In my case I first came to UK on student visa in Feb 2002. I switched from student visa to work permit on 10th April 2005 and thus my application is based on period of stay from 10th April 2005 to 9th April 2010.

Before my switching I visited Canada in October 2004 and returned on 22nd October 2004 back to UK.

So my first entry to UK would be the first day of work permit itself (i.e. 10th April 2005) or first entry before that which was 22nd October 2004.

Please advice.