The casual and general exercise of permitted development rights is always fraught with danger. Many people do not appreciate that each right has specific qualifications and conditions imposed on the exercise of those rights - and getting the interpretation of those factors wrong has serious implications. This risk is heightened when heritage assets are involved.
Fundamentally, as outlined in this article in the Guardian (and highlighted by the Private Eye before Christmas), it means that you cannot rely on the asserted right, resulting in unlawful development. This necessitates an application for retrospective planning permission (as is the case with National Highways here) to remedy the position, and retain the development sought. Please always check with a professional before undertaking such work - the fees may initially seem a waste, but the consequences of non compliance are far more costly.
This may sound strange, but what is encouraging here is the willingness of local authorities to assert their enforcement powers when it comes to unlawful development, particularly against a government entity. This sort of approach *should* breed confidence in the planning system, which (as much as it can be a pain in certain circumstances) can only be a good thing.
I am certainly not advocating for thousands of enforcement officers prowling the streets for breaches of planning control, but a confident, capable and assertive planning authority is key to the delivery of development and infrastructure. I am sure many developers would agree - though I am sure many would also say that it has been some time since they came across such an authority...
And so, as if often the case in planning, we come back to our good old friend: resourcing. Perhaps in the era of pork-barrel politics, we can pin that request on to the LURB?