It’s more like the last 5 years, and due to two high profile fatalities. As much as I like slam door/droplight stock, it’s not worth people dying over it. The rules are spelled out clearly, and if they aren’t followed then only the operator is accountable for that.
We all agree no one ought die. RIP.
But every decade your heritage trains (preserved and main line combined) carry a few million passengers.
Every activity in life has risk. Do we refuse to cross busy roads? Even at a pedestrian crossing with traffic lights, one can still get mown down if a car's brakes failed or a hoon drove at us. But we do a risk assessment for a microsecond, and know from past experience the benefits vastly outweigh the risks.
Do we ban car travel that has a far higher fatality rate per thousand journeys than heritage rail operations? Passengers can often open car doors in transit if they choose, but to do that would be idiotic, so it's rarer than hen's teeth.
I agree on main lines it can be dangerous to stick one's head out the window if there is an adjacent track with other trains potentially whoosing past at high speeds of say 130-225kmh or above (not high compared to true high speed rail, but still significant). Tunnels, overhead stanchions and some railside signs can be other dangers.
However, on branch or secondary main lines with lower speeds and fewer other trains surely there are fewer potential obstructions (except for tunnels). How many other trains is 'The Jacobite' going to cross?
Given what from my extensive travel occurs in other nations (India and Sri Lanka as extremes, where one can hang out of or in completely open doors, in India at up to c.100kmh), ORR's view seems a huge overreaction.
Just as the vast majority of air travellers aren't going to try to open an aircraft door even when the plane is about to land (as one fellow successfully recent did), provided conductors and car attendants check that slam doors are properly shut on departure, no one's going to try to open it when the train is moving, or after it's been shut.
Similarly, the prohibition on sticking one's head from the window of a door is overkill. USA-style paranoia, at least on secondary main and branch lines.
The greatest danger to Western socities is thousands of bureaucrats in multiple departments or agencies with nothing to do except think of more regulations/legislation that limit our freedoms.
"I'm from the government and I'm here to help you" is generally a big fib.