Speeding when overtaking?

Folks,

A quick question - if you pass a speedvan whilst over-taking, is this considered speeding?

The question is in relation to someone being over the limit during the overtake e.g. doing 110 to safely overtake someone doing 90 in a 100 zone.

This is a hypothetical situation that came up for discussion and none of us had an answer.

Secondary question - is it legal to surpass the speed limit to safely overtake as in the example above? (I.e doing 110 to pass in 5 seconds, rather than doing 99 and taking 20 seconds)

Thanks for any feedback,

P.