For years the traffic ran one way. British actors packed two suitcases, flew west and spent pilot season on a friend's sofa in West Hollywood. Somewhere in the past few years the current reversed. Ask any relocation agent, any international-school registrar, any estate agent working the leafier ends of north and west London: the Americans keep arriving, and they are not travelling light.

The reasons are boringly practical, which is why nobody makes films about them. Britain's soundstages are booked solid — the big studios have planted flags at Leavesden, Pinewood and Shepperton, and a performer chasing the biggest productions increasingly finds the call sheet says Hertfordshire rather than Burbank. Add schools that finish at a civilised hour, neighbourhoods where a famous face can buy milk unbothered, and a time zone that makes a European press tour survivable, and the move starts to look less like an adventure and more like arithmetic.

What the arithmetic never shows is the cargo.

A transatlantic move is disruptive for anyone. For someone whose working wardrobe carries its own insurance policy, it is a production in its own right. Twenty years in the business generates a strange inventory: award-night gowns worn for exactly four hours, guitars that have toured three continents, annotated scripts that auction houses would love to hear about, art bought in the flush years, gym equipment bought in the optimistic ones. None of it fits in a Notting Hill terrace. Little of it can be sold, because selling it feels like selling the career. So it all has to go somewhere — carefully, quietly and with paperwork.

This is where the unglamorous half of the entertainment industry earns its living. A whole ecosystem has grown up around the migration — the moving and storage services London now offers have learned to run like small production companies: schedules built around shoot dates, inventories managed to the box level, climate control for the things that warp and fade, and crews who understand that the first rule of moving a well-known name is that nobody finds out it happened. An unmarked van at seven in the morning does more for a star's privacy than any publicist.

Musicians may be the heaviest users of the system. A tour ends at Wembley or the O2, and it makes no sense to fly forty flight cases home only to fly them back in the spring; the backline winters in a warehouse instead. Actors run the same play between seasons: a character's world gets packed, labelled and shelved until the cameras need it again — or until the memorabilia market does.

Storage has quietly become the second act of every famous move. The London flat is smaller than the California compound — everyone's is — and the mathematics of square footage is undefeated. So the archive lives in a unit: the wardrobe a stylist raids the night before a premiere, the awards that would look like bragging on a shelf but feel wrong in a skip, the furniture from the old life nobody is quite ready to admit is over. People in the trade will tell you the units hold truer biographies than the interviews do. A career is what ends up on screen; a life is what ends up in boxes.

There is a lesson in this for the rest of us, and it has nothing to do with fame: the difference between a chaotic move and a smooth one is never muscle, it is admin. A real inventory. Photographs of everything before it is wrapped. Boxes labelled by room rather than by mood. Insurance sorted before the van arrives, not after. The famous simply pay to have that discipline done for them; the method itself is free to steal.

The premiere photo is the glamour. The machinery behind it is bubble wrap, a booked lift and a van idling in the London rain. Nobody posts about that part — which, the people who do it for a living will tell you, is exactly the point.