Millions of NatWest, Royal Bank of Scotland (RBS) and Ulster Bank customers are still counting the cost after a computer failure left them unable to access their cash. RBS Group chief executive Stephen Hester (right), in an open letter to our users, apologises and explains how he'll try to put things right. (Also see the RBS reclaiming news story to get charges back.)

I'm grateful for the opportunity to explain to users how RBS is working to put things right for our customers and to learn the lessons of our recent systems delay.

I am sorry for the unacceptable inconvenience this caused many of our customers. People rely on our bank every day to get the basics right. On this occasion, we let them down.

Our first priority was to help any customers experiencing difficulty. Over the past couple of weeks, we opened our branches for longer, doubled the number of staff in our UK-based call centres and gave staff greater authority to provide on-the-spot help.

This allowed most customers to get done what they needed, albeit with inconvenience.

Our frontline staff have been superb. This is a situation you would never wish for, and not a problem of their making. But in dealing with such a difficult moment, their commitment to our customers has really shone through.

Refund plans

We are now beginning the job of putting things right for customers who were unfairly impacted by this problem. We don't expect credit — this is a necessary step.

In the coming days, we will be adjusting the accounts of affected customers to put them back to where they would have been had this problem not occurred. As well as automatically refunding unfair fees or charges, we will credit any interest they were wrongly charged or should have earned. [MSE insert: see the RBS reclaiming news story for full info.]

We will ensure no customer's credit rating is affected as a result of this incident. We will work to set the record straight before any credit reports are supplied to Experian. And to give peace of mind, we're also writing to these customers with details of how they can receive a free credit check.

The next step is to put things right for people who faced knock-on costs during the systems delay. Those who incurred extra costs will be reimbursed, whether they are our customers or not.

We know there are customers of other banks who will have been affected and have worked closely with those banks to ensure they can resolve any such concerns. They should contact those banks about resolving their problems.

Our customers can get in touch by calling one of our freephone numbers (0800 656 9639 or 0161 931 9959, and 0800 231232 or 028 9084 3556 for Ulster Bank), visiting our website, or by speaking to staff at their local branch. In many cases, our branch and call centre staff can resolve people's concerns immediately.

In fact we are well advanced in these. Our dedicated response team has already resolved 90% of the 21,000 enquiries received so far. We will continue to work hard to resolve any issues promptly.

Ulster Bank problems persist

Regrettably, in Ulster Bank, our customers experienced problems with their accounts for longer than at NatWest or RBS. Fixing the issue for these customers has been a top priority for the RBS Group, and significant resources have been directed to Ulster Bank.

We have now largely caught up, and this week should be the final week of residual systems clean-up for these customers. We will then begin the work of putting things right for these customers too.

People will rightly expect a full account of what went wrong and what steps we will take to ensure it doesn't happen again. As soon as we have resolved the problems at Ulster Bank, we will begin a full and detailed investigation overseen by independent experts and reporting to the board's risk committee.

We will then make the improvements needed to ensure that future systems resilience is much, much better.

Finding out what went wrong

We know from our initial reviews the problem was created when maintenance on IT systems in Edinburgh disrupted the system that schedules the processing of around 20 million overnight transactions.

Many transactions failed to process on the night of Tuesday 19 June. The knock-on effects were substantial, and were compounded because the team could not access the record of which transactions had been processed up to that point.

It is not clear at this stage why that record was not available, and this will be an important question for the investigation.

But the time it took to resolve this initial problem created a huge backlog, and as a result many customer account balances did not update as they should have from Thursday 21 June.

Please help us help you

This past couple of weeks have created inconvenience for many of our customers. Their confidence in us has taken a knock. This has only increased my resolve to see through the job I joined RBS for — to transform us into a bank that always puts its customers first and serves them well.

Over the past three-and-a-half years, the team I lead have worked hard to make RBS a safer and smaller bank focused on the core banking services people need us to provide. Clearly we have more work to do.

This incident was a stark reminder of how our customers rely on us every day. I am determined that we win back their trust.

When we have finished the job of putting things right, we will also want to invite our customers to have a discussion with us about how we can do things better in the future.

I hope that and its users will also want to be a part of that feedback. Thank you again for this opportunity.

Views expressed are not necessarily those of