The blackout meant the 14 firms on the retail park missed out on thousands of pounds worth of trade on the busiest day of the week.

Businesses on the retail park were forced to close their doors when the power went off. Tesco was the first to reopen at around 12.15pm, using a back-up generator, before its power was restored. But all of the other stores remained in darkness.

The majority of other businesses were open by around 12.45pm. All power was restored to the area by 1.12pm.

A spokeswoman for McDonalds said they had their power restored but were unable to open for a further 45 minutes as they had to wait for equipment to heat up.

Tesco manager John Brooks said 300 customers had to leave the store.

He said: “We went on to a back-up straight away that enabled us to finish trading with the people in the store. We are still calculating how much we have lost.”

Danny Hadlend, manager at Instore, added: “Saturday is our busiest day when we serve around 1,000 customers so we would have lost a considerable amount.”

Alex Walker, duty manager at Homebargains said the store would have lost thousands of pounds.

Central Networks spokesman Jane Branscombe said: “It looks like it was just a fault. Our immediate priority was to get the power back on then we will investigate the cause.”

The power cut also hit the lights at Ketley Brook roundabout. Dave McNeil, 38, from Horsehay said: “It’s been a nightmare every morning since they were put in but for once on a Saturday morning traffic has been driving straight through.”