Getting an Image Full Width Across the Page

I want to make the topic image of this page full width, but it’s not doing it: https://www.varii-promotions.co.uk/edinburgh-promo-staff/

For this page it does work however; https://www.varii-promotions.co.uk/london-promo-staff/

Can anyone get this working for me?

Best regards,
Simon

A duplicate issue and I already replied to this thread Getting images full width