"CEOs don't get paid on popularity - they get paid on making the tough calls and making the tough decisions. So Ralph had a huge amount of courage to do that, I think."
Lark's aim is to remind people the value they actually get for their monthly bank fees. And he is hugely excited about various projects underway intended to ensure the bank is seen as the leader in its field.
In October the bank unveiled Kaching, a mobile phone application which allows customers to email each other money, as well as make payments through Facebook. The application also has a PayPass facility, meaning users can simply wave their phones over special terminals to make a payment.
"For me to email you $20 to send it to your phone, or to your Facebook account, it's game-changing," he enthuses.
Huge amounts of money are also being spent on data mining, says Lark. The bank has two main datasets - information about its customers, and real-time monitoring of their transactions, for security and other reasons.
"There's a huge amount of innovation in this space."
Meanwhile, banks are also eyeing the market for the storage of digital data as well as money.
Most of CBA's 10 million customers already use its online banking service, known as NetBank, and increasing numbers are using mobile phones as well. According to Lark, one noticeable trend is that many customers are now logging in with their phones while watching TV. In April, there was a huge spike of customers logging in during the British royal wedding - presumably doing a bit of banking during the boring bits.
Tracking these sorts of transactions in real time helps the bank roster staff more efficiently, he says.
Lark also notes that Facebook is still growing exponentially, and that two-thirds of New Zealanders are now believed to spend more than three hours a week on the social network. In Australia, the figure is believed to be 84 per cent, making Australia Facebook's third largest market by penetration.
As a frequent user of Twitter and other social media, Lark is excited about the possibilities for improving customer service through dedicated social response teams.
"One of the things that Ralph has done which is nothing short of remarkable is the turnaround in customer satisfaction," he gushes.
But of course, there is always room for improvement - this week thousands of customers were unable to access their funds due to a "network connectivity problem" which also affected eftpos purchases and phone banking. Twitter went ballistic.