My god, if ever there was a case for the study of confirmation bias, this is it. 
I relay how I, as an advanced driver was trained and advised by a guy who trains police drivers in their everyday (not only in emergencies DillyDally, where the heck did that come from?) correct defensive driving techniques, I pass on information and insight from officers, police driving instructors, advanced driver observers and examiners who all agree that passing on the inside is allowed, I highlight that the internet is full of discussions on this topic and the majority of advanced drivers agree passing on the inside is allowed, I point to the law which does not say passing on the inside is illegal no matter how many of you lie and claim it is, I ask you to cite the law that says it is an offence and not one of you can, I point out that not one single prosecution has taken place for passing on the inside as an offence, I highlight that the advisory paragraphs in the HC are not the law and are designed to advise you how you should drive and not how you must drive since it allows you to use judgement for the safety and stability of your vehicle precisely because the HC does not provide every scenario of what you should do when you come across a law-breaker such as middle lane road hogs and yet still some of you scour the internet desperately to search for a post or a reply which confirms your preconception that passing on the inside is illegal or wrong. Absolutely desperate to ignore anything which is against what you want to believe. Search and search until you find one piece that agrees with you. Ridiculous.
The aggression and bulling on here has been unbelievable. The hypocrisy, merely laughable. The obsession with section 268 almost manic and your avoidance of section 264 notably laughable: "You should always drive in the left-hand lane when the road ahead is clear." What about that then? Stay in your lane, keep your car stable, do not put yourself at additional risk by overtaking a middle lane hogg, and proceed with caution to pass the hogger on the inside staying in your lane as per 264. But oh no, let's pretend that doesn't exist eh?
That post with the reply from the single police officer is a joke. The officer claims undertaking is an offence, when it is not. They can't even get that right. The poster asks the question on a clear motorway and the officer says they would charge them. They would be laughed out of court. I ask again - show me one single case where this correct (ie cautious) passing on the inside of a middle lane road hog on a clear motorway scenario has been successfully prosecuted. Just one. Show us all and make your case then.
Drivers pass on the inside every second of every day. They are passing middle lane road hogs, or passing slower moving vehicles and queues in the lanes to their right. Some of you claim the 'congestion' word in 268 means 'crawling' when it doesn't. So how come thousands of drivers pass others on the inside in both variable and non-variable speed limit motorways every day without one single prosecution? It is called maintaining your speed and driving correctly. But some of you believe drivers should be constantly slamming on their brakes each time the lane to their right suddenly slows just so you don't end up passing on the inside. Can you imagine the chaos? Crazy.
I am sorry that some of you do not want to believe something is different to what you thought. I am sorry that some of you don't understand the premise of the Highway Code nor how it should be used and how it was written. I am sorry that some of you do not understand the law. I am sorry that all the information given here doesn't give you the answer you crave. I am sorry that you find my disagreeing of you so deserving of ad hominem attacks and vulgar language against me and relentless animosity despite my attempts to be polite and still answer those who have insulted me horribly.
I cannot understand the behaviour of some of you, I really can't. Go ahead and believe what you will. But stop claiming manoevres on the road are illegal when they are not, and if some of us pass middle lane hoggers on the inside with caution to maintain our driving line, stick to 264, and not waste our time or risk ourselves by doing 4-6 lane changes, we shall continue to do so.
I repeat one final time. Nowhere does it say it is illegal to pass on the inside. Nowhere. And the authorities took away the offence of undertaking in 1972, and passing on the inside is allowed, for a reason.