WW1 War Diaries - The National Archives

Is to digitise unit war diaries from WW1. They are looking for volunteers to help
http://www.nationalarchives.gov.uk/news/625.htm

[Kit]

I was going to say I can't help I'm too far away but they say this:

All volunteers will have to pass our security clearance, and we can offer basic travel expenses.

I wonder if Oz to the UK would count as a basic travel expense?

I also wonder what the security clearance consists of and why it would be necessary.