Legacy TV’s and set-top boxes, (approx. pre-2013), and devices with no Internet connection capability are unable to support the required HbbTV standards necessary to operate interactive TV applications such as UK Radio Portal.
Prior to the HbbTV standard was a technology called MHEG-5, which was developed in the mid-90’s. This older technology is unsupported by UK Radio Portal, and unconnected/non-connectable devices of this generation will display a black screen when tuned to UK Radio Portal
Legacy MHEG-only devices with Internet connection capabilities will be presented with a more graceful message, as shown below, advising users that UK Radio Portal is unavailable to these TV’s or set-top-boxes. Unfortunately, the only way to overcome this issue is to invest in newer generation TV with HbbTV support.
For interested readers, as article from informitv title “Moving On From MHEG” can be found here.