Lauren (left) and Abbey were thrown from the car

Heather Thompson, 41, was driving at up to 80mph as she took the two girls to a birthday party.

Abbey Thompson, who was celebrating her 12th birthday, was killed along with her friend Lauren Wheeler, 12.

Thompson, from Woodhall Spa, Lincolnshire, told police the girls had laughed as she sped along the bumpy road.

A judge at Lincoln Crown Court heard Thompson had collected the two youngsters from drama lessons in Bracebridge, where she had told other parents she could travel the 15 miles to Woodhall Spa in only 15 or 20 minutes.

She was travelling through Martin Fen last June when several witnesses reported her overtaking a number of cars at high speeds along a bumpy section of the road.

The car came off the road at over 70 mph

Gareth Wheetman, prosecuting, read a number of statements from drivers, who reported that she was going too fast.

Witness Nigel Bryant estimated the silver Rover 216 was being driven at speeds in excess of 80mph which was "reckless and stupid".

He watched as the car flew into the air and turned over and over before landing upside down in the ditch.

The defendant was found to be crawling out of the driver's window, hysterical and crying: "I just lost control, I just lost control."

Mr Wheetman said the children were later found in a ditch and although people at the scene tried to resuscitate them, they both died.

The sad fact is that all too frequently I have to sentence drivers for causing death by dangerous driving Judge Michael Heath

A forensic examination of the scene of the accident found the probable speed of the vehicle at the time it went off the road was 72mph.

Thompson told police in interview how the girls were laughing because they had hit bumps in the road but when she suddenly lost control she heard Abbey cry: "Mummy please stop it."

Kaiser Nazir, defending Thompson, said: "Mrs Thompson has never attempted in any way to lessen her guilt for this incident."

Thompson was led away from the court shaking and weeping after being jailed on Monday.

'Human tragedy'

Outside court Lauren Wheeler's mother Debbie said: "Our lives, our futures have changed completely. If only she'd just done something different, and not driven so fast."

Judge Michael Heath, sentencing, said: "The sad fact is that all too frequently I have to sentence drivers for causing death by dangerous driving.

"Each case is a tragedy and every time I deal with such a case I hope that drivers in Lincolnshire will harken to the severe human tragedy that these cases bring and henceforth drive appropriately so that these cases are reduced."

Thompson, who pleaded guilty to two counts of causing death by dangerous driving, was sentenced to two years on each count to run concurrently.

Outside court, her solicitor, Ros Danson, said: "No order or sentence passed by the court could ever be greater than the sentence Heather has given herself."