Published Wednesday, 05 December 2012
Model Twiggy and Samantha Cameron, the wife of Prime Minister David Cameron, were also among the guests of honour at investment firm ICAP, which donated Wednesday's entire revenue to good causes as part of the company's 20th annual global Charity Day.
The stars manned the phones to help close deals alongside ICAP employees, who donned fancy dress for the occasion.
Hawn loved her time in the office, telling fans in a post on her Twitter page: "I had a blast!"
Pregnant British royal Catherine, Duchess of Cambridge had been due to attend the ICAP event, but she has cancelled all her engagements as she remains in hospital receiving treatment for a severe bout of morning sickness.