Tens of thousands of tube commuters are being affected by a train shortage caused by 'leaves on the line'.
More than a tenth of the Piccadilly Line train fleet is out of action because of emergency repairs to damaged wheels.
The 40-year-old trains lack modern systems to stop the wheels sliding on slippery tracks coated in wet leaves.
The train shortage has led to a week of misery for passengers on the line from Heathrow Airport to Cockfosters.
Underground managers need around 80 trains to run a full rush hour service but are having to rely on just 70.
In Autumn and Winter in changing conditions but particularly in heavy leaf fall periods our trains struggle to grip, particularly when braking.
Engineers using a special lathe take three days to repair the 48 wheels on each train.
LU said it planned to hire in a second lathe next week to speed up the process.