An e-bike conversion kit is available for Brompton bikes from the brand Byqee. The lightweight and compact kit provides a motorized rim, battery, controller and pedal assist sensor, allowing you to electrify your folding bike. Features include 350W peak power and a 40 km (~25 miles) assistance range. Plus, the model is currently discounted.https://www.notebookcheck.net/Byqee-e-bike-conversion-kit-for-Brompton-now-available-with-discount.801949.0.html
I had a conversion kit on my Brompton, and the fork gave way, was told it was designed or strong enough to be used with the motor