Part of NHS architecture principles
Reuse before buy/build
Digital services should demonstrate that they have sought to reuse existing solutions before delivering new ones.
Where it is not possible to reuse an existing solution, off-the-shelf (commercial or open source) products should be considered. For open source products there should be an appropriate level of contractual support provided.
Only having ruled out the former two options should a new solution be built, either in-house or through third parties.