What is it?
The Fiesta is the latest to receive battery assistance, joining the Puma and Focus with a 48V architecture that promises to bring modest fuel and emissions savings to the (already rather efficient) 1.0-litre three-pot Ecoboost petrol engine.
It's a familiar set-up, with a belt-driven starter motor feeding in extra torque courtesy of a small lithium ion battery that relies entirely on regenerative braking to charge itself. This combination cuts down on turbo lag, lets the stop/start system activate while coasting below 15mph and makes acceleration that little bit peppier. It has also allowed Ford to add a larger turbocharger and lower the engine's compression ratio, for what it claims are 5% efficiency gains over a non-hybrid engine.
The battery introduces only a minor weight penalty, so performance remains largely unchanged, with 0-62mph in 9.4sec and a top speed of 126mph. There's a slightly nippier 153bhp version that dips under nine seconds, but neither can be had with an automatic transmission.
Mild-hybrid power arrives as part of a wider update for 2020, which sees all Fiestas with Cross Traffic Alert gain active braking, and ST-Line models like our test car get a perpendicular park function for the active park assist. The optional B&O Play sound system also has its subwoofer relocated, so you no longer have to choose between banging tunes and a bit more boot space.