A new report finds no physical constraints to extending the Northern line one more stop.
We've all speculated and asked the question: why did the 2021 Northern line extension stop at Battersea Power Station and not go that little bit farther to Clapham Junction?
It seems obvious. Clapham Junction is one of the busiest stations in London, serving dozens of mainline trains an hour, alongside two branches of the Overground. Not to mention all the buses. Why not plug in the Tube as well?
Calls for further extension have now been taken forward by the local authority, Wandsworth Council. It wants to increase transport capacity in the area, and also unlock development potential around Clapham Junction. To that end, the council commissioned an investigation into the feasibility of building such a link. This has now been reported, finding "no engineering or geological constraints" that could scupper the idea. Thus emboldened, the council will now conduct a public consultation to gauge public support.
So why didn't it happen first time round?
This lack of connection has long been a grumble for those who live in the area. "Fury" was the word used by the Daily Mail (because of course it was) when the extension opened in 2021 without a Clapham Junction link.
The reason is a complex blend of factors. Cost is the obvious one. Much of the money would have to come from developer contributions, which would require huge redevelopment at Clapham Junction. Never easy to get through planning.
Fears of swamping the Northern line were another issue. So many people pass through Clapham Junction that the expected crowds could prove overwhelming. Previous studies anticipated the need to upgrade the Northern line, by remodelling the rate-limiting junction at Camden Town, and splitting the branches into two separate lines. This would improve capacity, but come at great cost. However, the crowding problem may now be less severe given the dip in passenger numbers since we all got fond of working from home.
Finally, there's Crossrail 2. This long-planned north-south underground route would stop at Clapham Junction. Plans remain on hold but, were it to be built, any business case for extending the Northern line would diminish.
Wandsworth's investigation and consultation will not solve all of these objections, but they do keep the idea alive and in the public eye. Transport for London built the 2021 extension with an alignment that would support a future push to Clapham Junction. It could happen, one day, but for now the Clapham Junction extension remains a pipe dream.
