There are numerous digital marketing companies London, as it's a major hub for marketing and advertising in the UK. Here are some well-known digital marketing companies in London, as of my last knowledge update in January 2022. Please note that the landscape may have changed, and new companies may have emerged since then.

• BBH London: Bartle Bogle Hegarty is a global advertising agency with a strong digital marketing presence in London.
• Ogilvy UK: Part of the Ogilvy network, Ogilvy UK offers a wide range of digital marketing services.
• Wunderman Thompson: A global marketing communications agency with a strong digital focus, they have a London office.
• VCCP: A creative advertising agency with digital capabilities, VCCP is based in London.
• We Are Social: A global agency specializing in social media and digital marketing with a London office.
• iProspect: A performance marketing agency with a strong presence in digital advertising.
• Croud: Croud is a global digital marketing agency with offices in London, offering services like SEO, PPC, and more.
• AnalogFolk: A digital creative agency that focuses on creating connected brand experiences.
• MediaCom: A global media agency with a London presence, offering a wide range of digital marketing and media services.
• Wavemaker: Another major media agency with a strong digital focus and a London office.