The practice has been commissioned by Better Bankside, a district-improvement firm, to effectively link two of south London's largest developments, Make's Elephant and Castle regeneration and Herzog & de Meuron's Tate Modern extension.
The park will extend southwards through Southwark, connecting newly developed areas with soft and hard landscaping and improving the urban realm with pocket parks and other small-scale developments.
WWM director Stephen Witherford said: 'It's very exciting that a young practice like ours has been trusted with this challenge.
'I was involved in the Architecture Foundation's Future Southwark initiative 10 years ago and it's amazing to see not just the transformations the area has accommodated, but also what has endured.
'We are really looking forward to working with the stakeholders and residents to further explore the dynamics of the area.'
WWM was selected following a tender process, which attracted expressions of interest from 11 different practices.
Donald Hyslop, chair of Better Bankside, said: 'The expectations from the brief are complex and reflect the number of interests which are party to the study.
'WWM produced a considered approach that addressed the challenges and opportunities that exist.'
The masterplan and framework for the scheme are due to be completed in early 2007.