Owen Sharp, chief executive of the now rebranded Prostate Cancer UK, says the fundraising teams for the two cancer charities had worked together previously on smaller events and were hoping to do so on a bigger scale when the opportunity arose to bid for the marathon, which took place in April.
They thought that a collaboration would appeal to a wider demographic. Sharing the bidding process would also incur lower costs and pooling the creative minds from two organisations would bring energy and drive.
"We agreed at the outset that there would be a 50:50 split in terms of the effort put into the process and the money raised, and we stuck to this," says Sharp. "In reality, there is no precise way of measuring the workload: at times, one charity's department had more capacity so it would take on more of the work, but this evened out overall. Both charities believe that input and output were evenly split."
The charities developed the concept of collaborating under a Team PB banner - standing for Team Pants and Bra. This played on the Olympics' Team GB, which Sharp thinks appealed to the marathon organisers. "It was a new idea to bring together two organisations that had a good balance," he says. "Our colours, pink and blue, and the pants and bra theme, which was fun and goes well with the marathon ethos, all worked together for a good pitch.
"It worked well for us to create a separate but joined-up identity that everyone could feed into. Everyone felt a part of Team PB."
The partnership brought together two charities with shared aims, but Sharp says it did not cause any conflict because his charity's cause area affects only men, whereas breast cancer is predominantly a female disease. "We were excited to have won the bid for the marathon in the Olympic year," he says. "It was widely recognised that this could have been achieved only in collaboration - we were not ready as individual organisations."
But he admits to some teething problems. "Despite all the energy, goodwill and positivity, we were bringing together two culturally different organisations - and that had to be recognised," he says.
"We made the effort from the start to bring together the two fundraising teams on a number of half-day awaydays. We needed to have a clear decision-making process and strong project management was needed from outside. There was only one shot at getting this right and the project manager needed the experience and ability at a senior level so that decisions could be made from a neutral perspective."
Sharp says that clear and consistent communication between the two organisations was vital: rather than drawn-out meetings, they aimed for regular "punchy" ones.
Sharp says the collaboration was a huge success - 830 runners completed the run on behalf of Team PB and raised a total of more than £1m for the charities. He says his charity wants to work with Breast Cancer Care on legacy events and programmes in the future.