He also stated that although the thought of cloud made many within the business "go pale in the face", the platform is running to service levels beyond what Mortimer was able to agree with Salesforce's commercial team.
"There were a number of concerns around cloud, not just the security element. This is business-critical activity and uptime is essential - this was clearly a big leap of faith," said Mortimer.
He added: "I tried to demand high service levels from Salesforce, but wasn't able to agree targets with the commercial team.
"However, we are actually operating to levels much higher than what I attempted to agree - we are operating at beyond 99.9% uptime.
"We have been using it for the best part of a year now and we haven't had an outage yet, which isn't what you expect from new platforms and new technology. Typically what you would be looking at is hundreds of minutes of downtime and how you would reduce that."
O2 also recently announced that it has signed a five-year managed services deal with China-based services provider Huawei. It will be transferring 118 staff to work for Huawei's managed services business, where under the agreement, Huawei will be charged with planning, implementing and managing Telefonica's core transmission, mobile access and network in the UK.