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Thanks for your answers guys. . Nobody is talking about deliberately BLOCKING the lane, just carrying out a perfectly safe, and legal overtaking manouvere and being tailgated and flashed by Mr Impatient whilst doing so. I think we all know the sort of drivers were talking about here, without being smart.
No police car, or emergency vehicle would ever tailgate, and sorry but family emergencies do not qualify drivers to break the law. I have a 97 year old family member, so know about 'emergency calls' but I still have to drive the 85 miles to the hospital without speeding or being a pain to other road users.