Mobile phones being used in Didcot
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Mapping Britain's 3G mobile data networks: Oxfordshire

A BBC crowd-sourcing survey to map the UK's mobile phone networks has revealed the parts of Britain where mobile phones can only receive slow 2G data signals.

Users of more than 44,000 phones downloaded an app to measure data speeds over a month.

The software helped build an interactive map which lets people check reception at specific postcodes.

Rory Cellan-Jones took a train journey from Cardiff to London to test data speeds along the route.

He stopped off in the Oxfordshire village of Cuddesdone, where it seems most mobile phones can only receive sluggish internet signals.

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