Images 'stuck' inside frame by default

Hi.

Currently having some issues with image sizing in posts. All images appear within a ‘frame’ and regardless of what I do (adding as full sized, custom sized, uploading from external link rather than media library) I’m unable to change the sizes of them in any way on page.
Link for ref:
http://www.eventa.co.uk/news/team-building-2/how-the-rugby-world-cup-has-inspired-eventas-team-building-3248

Any ideas? Is there something obvious that I’m missing? Anything more you need to know?

Many thanks