The authorities would like to thank him for his prompt actions.

The man used a ladder on the back of his lorry to help the family climb down from a roof on Welford Road.

It is thought someone deliberately set fire to outbuildings behind their home.

Severe damage

The man was the first to alert the emergency services to the fire which destroyed outbuildings at the back of shops on the Welford Road.

The family, who lived in a flat above the shop, had already managed to climb out of a window onto a flat roof when the passer-by helped them down using his own ladder.

He then disappeared without leaving his name or address.

A fire service spokesman said: "Damage to the outbuildings was quite severe.

Suspicious cause

"Smoke from the fire had got in to the house and fire crews had to use breathing apparatus to tackle the blaze."

Leicestershire police would like to trace the passer-by to thank him for saving the family of two adults and two children, none of whom were hurt.

The fire started just after midnight.

Police have confirmed they are treating it as suspicious.