Excellent video. Lest anybody gets confused, DLR stands for Docklands Light Railway. It is similar to many Light Rapid Transit systems in operation worldwide, mostly at airports as well as other densely populated areas or regions without adequate population to justify a full-fledged metro operation.
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While the trains are indeed capable of running automatically (known at ATO - automatic train operation), the trains can still be run manually by an operator inside the train. At peak times, you will see staff inside the train, ready to takeover from ATO to manual operations...
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in case there is some glitch.
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Also, DLR operates in some areas along the Thames riverside and associated estuaries where the terrain may not permit the kind of infrastructure required for the regular London Underground. Some of these areas are in central London too e.g. Bank and Tower Gateway.
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On a slightly unrelated note, the Singapore implementation is particularly fascinating where the side-windows turn from transparent to opaque every time the train comes too close to a residential building to protect the privacy of building occupants.