Kantar CEO Eric Salama, 57, was attacked just before 8am on Sunday after finding a suspect trying to steal his car outside a cafe.
He suffered a stab wound to the chest and crawled back to the cafe for help, where he was treated by paramedics.
He is said to be in a stable condition in hospital with non-life-threatening injuries.
Salama is the CEO of global marketing firm Kantar TNS and has previously served as an advisor to the Government on e-commerce and business.
A spokesperson for Kantar said: “We can confirm that Mr Salama was involved in the incident in Kew at the weekend. He is recovering well and our thoughts are with him and his family.
We would like to request privacy for the family at this time.”
Speaking to the Daily Mail, shop owner Fasink Nizri said: “It happened in a matter of minutes – two minutes – I saw blood, there was screaming. Eric is a decent man and has no problems with anybody.”
“The person tried to steal his car; he asked ‘what are you doing?’ ‘He was stabbed just near his heart, it was very bad – the knife was enormous – he was hit so hard that the knife it bent.
‘Our staff managed to stem the bleeding, then we called his son and an ambulance, it was terrible, terrible.”
No arrests have yet been made.
The Drum reports that Salama had been discussing a potential £3.5bn management buyout of the data and market research company in a possible split with parent company WPP.