The throttle is an option which on the standard Panasonic units produces the EU regulation 6 kph (3.6 mph) for walk alongside purposes. In Britain and the EU this is legalised by the Pedestrian Controlled Vehicle legislation, covering such as the electric barrows used by the Post Office. Using the throttle while riding isn't covered of course.
When that same throttle is connected to the S high speed unit models from Kalkhoff and Flyer, the speed capability jumps accordingly to around 11 to 12.5 mph, according to the bike gear set, a by-product of the faster unit.
So more a run alongside throttle and illegal in the EU including Britain. Still, the whole bike is illegal in those areas, except Germany where there's a high speed class, so not worth worrying about just the throttle.
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