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There are the XP diehards, and the Windows 7 and 8 migrators. But in a world facing up to the end of Windows XP support, one UK organisation belongs to another significant group — those breaking with Microsoft as their principal OS provider.

Microsoft's end of routine security patching and software updates on 8 April helped push the London borough of Barking and Dagenham to a decision it might otherwise not have taken over the fate of its 3,500 Windows XP desktops and 800 laptops.

"They were beginning to creak but they would have gone on for a while. It's fair to say if XP wasn't going out of life, we probably wouldn't be doing this now," Barking and Dagenham general manager IT Sheyne Lucock said.

Around one-eighth of corporate Windows XP users are moving away from Microsoft , according to recent Tech Pro Research.

Lucock said it had become clear that the local authority was locked into a regular Windows operating system refresh cycle that it could no longer afford.

"If we just replaced all the Windows desktops with newer versions running a newer version of Windows, four years later we would have to do the same again and so on," he said.

"So there was an inclination to try and do something different — especially as we know that with all the budget challenges that local government is going to be faced with, we're going to have to halve the cost of our ICT service over the next five years."

Barking and Dagenham outsourced its IT in December 2010 to Elevate East London, which is a joint-venture between the council and services firm Agilisys.

Lucock and systems architect Rupert Hay-Campbell are responsible for strategy, policy and investment while Elevate looks after delivery.

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"We asked Elevate to carry out a fairly detailed options appraisal of what the possibilities were. What we did realise was that we couldn't keep on doing ICT in the same way we had done before," Lucock said.

Three options were on the table. The standard approach was just to replace most of the XP desktops with a newer version of Windows. Because the council bought out of its Microsoft Enterprise Agreement a couple of years ago, it has perpetual licences that cover it up to Windows 7.

"Windows 8 would not have been an option for us because that would have required a significant reinvestment in Microsoft licensing. So that was one of the options — just do more of the same but with a newer version of Windows," Lucock said.

Then there was the possibility of repurposing much of the existing hardware as thin-client terminals, investing in new thin-client terminals and then running Citrix XenDesktop or VMware Horizon VDI.

"That wasn't going to address the mobility and flexibility issues and that would have meant we would have been wholly dependent on our virtual desktop infrastructure for evermore, because that's all the clients could have used," he said.

The third and eventually successful option was to look at Chrome OS and in particular Chrome Books and Chrome Boxes.

"There are a number of advantages there. One is that it's a browser and not just a thin client. So initially the Chromebooks and Chromeboxes will be used as thin-client terminals accessing published applications through Citrix," Lucock said.

The user experience would be little different from that under XP, with a Citrix storefront login screen taking them to familiar mapped drives and apps such as Office 2007.

However, because of the native Chrome browser, the council's ultimate aim is to move as many of its office productivity systems such as email and calendaring away from the Citrix infrastructure and into the browser through software as a service or the cloud.

"So in a sense it was a strategic move. Initially, there is very little change. Everyone is using the applications that they were using before in the same sort of way in Citrix," Lucock said.

"Over time, the native browser of the Chromebooks and Chromeboxes will be the predominant method of access to what people need. That was something the thin-client devices didn't have — it's a fundamental difference between those two options.

"Obviously, we'd need to look very carefully at the offerings from both Google and Microsoft but we'd certainly be wanting to move as much as we can out of Citrix onto the browser in the shortest possible time."

Google Apps reseller Ancoris was brought in to support Barking and Dagenham through a number of evaluations and pilot projects last year as part of its due diligence before the council opted for Chrome OS.

The initial rollout of 1,500 Samsung XE303 Chromebooks is taking place at a rate of several hundred devices a day, with the migration due to be completed by about the first week in June.

Lucock said the interval between the end of XP support and the June completion date represents an exceedingly low risk because of the strict security policies already in place.

"We have a very tightly-managed XP desktop estate that we were starting with, with end-point management on all devices and so on. So we're fairly confident we can get through to the beginning of June without any issues," he said.

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"Ideally, we would have squeezed that time period a little bit more but we're not unduly over-worried that there's suddenly there's going to be a huge issue."

On top of cost savings of about £200,000 ($340,000) over the cost of new Windows desktops, Lucock said there are other advantages in the Chromebooks approach even though it has entailed upgrading wi-fi across council buildings and investing in the Citrix infrastructure to spec it for 3,500 people.

"It's cheaper to supply a Chromebook than it is a Windows desktop, not only in the capital cost of the equipment but in the deployment and the rollout," he said.

"It's very easy to roll out ChromeOS devices. You just take a note of who you've given it to and hand it over."

Ongoing support is also going to be much less onerous and expensive, with no need to worry about patches and antivirus, or keeping multiple images.

Power savings could amount to a further £200,000 ($340,000) because of the greater energy-efficiency of the Chrome OS devices.

Chromeboxes are being deployed as fixed devices in kiosk and hotdesking areas. But wherever a device is being assigned to an individual, it will be a Chromebook.

The council will still be running as many as 600 Windows 7 machines for applications such as AutoCad that demand it and for special hardware requirements.

"But the fundamental difference here is that we've switched it around so the default is always going to be the Chromebook. Then if there's a particular reason why that's not going to work, we do something different," he said.

Although without the end of XP support Barking and Dagenham could have stuck with the 12-year-old operating system, Lucock is pleased to be making the move.

"With the benefit of hindsight, I'm glad that we are because we had a very sedentary workforce. We had 3,500 employees and we had 3,500 desktop machines. If people needed to work in a mobile or a more flexible way, then we needed a laptop for them as well. So we had more devices than we had people," he said.

"We know we've got to rationalise our accommodation. We currently work from around 60 sites in a very small borough. Clearly, that's costly. We need people to work much more flexibly, with mobile to be much more a daily feature of people's lives."

The main benefit for the council lies in creating a more flexible workforce, Lucock said.

"Every time we replace a Windows PC with a Chromebook, we've enabled them to work anywhere. That's a big step forward — and to able to do that on such a large scale over a very short period of time, it's very exciting."