The agency will provide PR counsel and media outreach services to SNR Denton, which is set to become the seventh largest law firm in the world by headcount after agreeing a merger with Salans and FMC Law late last year.
The new firm will be called Dentons and will employ about 2,500 lawyers and professionals across the globe, with £1.3bn of revenues.
WS’ London practice will initially support the legal firm through its merger and then build the brand in Europe.
WS won the business via a three-way pitch and worked with SNR Denton on the initial merger announcement and messaging. The legal firm previously used Citigate Dewe Rogerson.
Jon McLeod, chairman UK corporate, financial and public affairs at Weber Shandwick, will handle the account, working with co-head of financial services Alex Brown.
The agency will report to Louise Ray-Hill, senior PR and comms manager EMEA at SNR Denton.
The integrated firm will have its largest base in London, though it will operate without an official HQ from major hubs in London, New York, Paris and Toronto.