Grinning from ear to ear, this picture shows little Leo Hargreaves was rather happy with his world – even before he was born.

And his parents believe their son may be the happiest baby in Britain as he hasn’t stopped smiling since.

The remarkable image was taken from an ultrasound scan at 31 weeks.

His mother Amy Cregg, 24, said: 'My partner Leighton and I were absolutely shocked - even the people who did my scan were amazed.

'But that was just the beginning. After he was born, he was always smiling - even in his sleep.'

Now nearly five months old, Leo has been dubbed the happiest baby in Britain.

The image is a 4D scan - increasingly popular with expectant parents to get a glimpse of how their child will look.

Rather then the grainy ‘flat’ images produced by the 2D scanners usually used by the NHS, a 4D machine stitches together pictures taken from a variety of angles to create clear three-dimensional images.

These are then recorded on video – the fourth dimension.

Ms Clegg, from Accrington, Lancashire, said she has already had modelling companies approach her trying to capture Leo’s smile.

The rehabilitation support worker said: 'I’ve been walking in the park and had people come up to me and say "What a gorgeous baby".

'I’d be interested in him doing modelling but only when he’s older.'

A spokesman for the company that performed the scan, at Babybond Ultrasound Direct in Burnley, said: 'Our sonographer who scanned Amy and her gorgeous baby was overwhelmed at her smiley baby throughout the entire scan.'

4D scans are a highly developed form of traditional ultrasound where very high frequency sound waves are used to produce images of what is inside the body.

As with older forms of ultra-sound, sound waves a emitted from a transducer, or probe, which is placed on the mother's abdomen and then moved to 'look at' areas in the uterus.

These sound waves bounce back off the foetus, helping to create a 'picture' of the child on a screen.

4D scans use the same frequency of sound waves as in a normal ultrasound.

But the sound waves are directed from many more angles, producing a 'real-time' video of the foetus as it moves and allowing scientists to say the images are in four dimensions.