Re: declaring language in html/xhtml

This may seem a strange question but it occurred to me during these 
discussions:

Consider a parallel text, such as the www.dvla.gov.uk (which is dual 
English/Welsh)

1) How would someone tag a web page's primary language when it actually 
has multiple ones?

2) Also, how should the language of a link to such a page be expressed 
with the hreflang attribute?


If I were a linguist that produced a page which was correct in both 
Australian English and British English, but not American English, how 
should it be specified?

-- 
David Clarke