The batteries, supplied by Power Cell, last around five years, with a four-plus-one-year warranty.

Smith admits that the company is “some way off” introducing lithium-ion technology.

“There is an advantage in the power-weight efficiency, but for us the development costs of the vehicle and what we are already achieving with lead acid, plus the payload we require of a vehicle , means lithium isn’t for us at the moment,” he says.

He did carry out trials of the Smith Edison Transit; they resulted in an average range of just 40 miles, 10 fewer than that achieved by the AC motors on the existing fleet.

And with a life expectancy of seven years, the cost calculation didn’t stack up either for the Transits.

Dairy Crest owns all of its EVs, although it has not bought a new one since 2005. Loughton Motor Bodies build the cabs, while Dairy Crest buys in the chassis and assembles the new vehicles in-house.

The major components can be refurbished or bought new.

In-life upgrades have included adding electrical elements such as speedometers to comply with 20mph zones, LED indicators, side and stop lamps, alarms and reversing sensors.

Dairy Crest’s non-electric fleet is on a more conventional leasing contract with Lex Autolease on full maintenance, except tyres which are on a separate deal with ATS.

The operating cycle has been reduced from six-plus-one-year to five-plus-one – the one being the option of a secondary lease if the vehicle still has life left. “It’s driven by age profile and to help manage dilapidation charges,” Smith says.

Crucial to ensuring life longevity for every vehicle on the fleet is Dairy Crest’s rigorous maintenance programme.

Everything is maintained on a rigid preventative maintenance inspection (PMI) schedule that mirrors the standards more commonly found in HGV fleets.

Vehicles with a gross vehicle weight of 7.5 tonnes and above are inspected every six weeks; EVs are inspected every 10 weeks; 3.5 tonne vans every 13 weeks; and car-derived vans every 26 weeks or sooner depending on mileage.

This schedule requires a close watch on variable servicing intervals; Dairy Crest has to make judgement calls on oil changes to prevent one occurring between inspections, creating unnecessary downtime.

Management of the PMI schedule is based around stickers on the back of every vehicle.

Each one displays a number which relates to the week when the next service is due, and every depot uses the same system.

This number must be checked against an atomic clock in each of the depots to ensure that the vehicle is still within its PMI schedule.

“It’s the kingpin of our safety programme,” Smith says. “We’ve got to be compliant; there is no place for people that do not operate commercial vehicles in a compliant manner.

"If you have a 3.5-tonne vehicle that is not inspected and maintained properly, it’s a disaster waiting to happen.”