The stunt marked the launch of the one-day conference, now in its fifth year, took place in Bristol for the first time this week.
Organised by Dods, which specialises in government and parliamentary events, four Royal Marines abseiled the Grade II listed building, accompanied by a four-man military band.
Christina Hunter, head of government events at Dods, said: "It was great to have the Royal Marines involved capturing the imagination of delegates on arrival with their breathtaking demonstration, ensuring the day started with a bang."
Following the military stunt, the event included a Question Time session with a panel featuring the BBC’s new head of strategy, James Purnell, and Olympic gold medallist, Katherine Grainger, as well as recorded videos by Prime Minister David Cameron and deputy PM Nick Clegg.
Naomi Easy, sales and conference manager at Colston Hall, added: "Hosting Bristol’s first Civil Service Live was a huge testament to the venue’s value within the region as a versatile large events space."
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