The Said protest contributed to rush-hour traffic chaos for thousands of motorists today.
The partial closure of Park End Street caused queues to build up along Botley Road and Oxpens, with traffic slowing to a virtual standstill.
Drivers attempting to enter Oxford via the A34 found themselves stuck in miles of tailbacks.
The hold-ups on the A34 in turn caused jams on the M40 as drivers queued to leave the motorway southbound at junction nine near Bicester.
Police blamed the "sheer weight of traffic".
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