OVO Energy
I worked on OVO Energy in the early days after their first rebrand. I was tasked with their Home Movers direct mail acquisition campaign. After a bit of research, we found that new movers were often put on a Standard Variable Rate by default. So, we told them about the SVR and gave them moving essentials, like OVO-branded moving stickers. It worked so well that they ran it unchanged for two and a half years.