Police were today forced to free a child from a sweltering car on the hottest day of the year - after a woman left the youngster for 40 minutes while she went shopping.

Panicked shoppers called officers after loudspeaker calls for the woman to return to her vehicle, which was left in a disabled bay outside a Next branch in Watford, went unanswered.

One onlooker told how passersby were 'screaming' at security guards to do something to release the child as the temperatures outside the vehicle soared to above 30C.

A woman allegedly spent 40 minutes looking around a Next store in Watford and was called several times to return to her car and child

The woman allegedly looked around the shop at Waterfields Shopping Centre and was asked to return to her car (left)

Police arrived and got the young child out of the Nissan vehicle, which was parked in a disabled bay at Waterfields Shopping Centre

The onlooker told MailOnline: 'An elderly woman was on the scene and screaming at a security guard to do something and let the child out.

'There were quite a few people looking on as the police arrived.'

Officers called to the scene eventually freed the child from the white Nissan Qashqai - one onlooker said it appeared the door was able to be opened from the outside without damage.

And after the child was released, the driver returned to her car having apparently been shopping the whole time at the store at the Waterfields Shopping Centre.

The onlooker added: 'All the woman got was a ticking off - it must have been unbearable for the child.'

A Hertfordshire Police spokesman said: 'Police were called at 12.40pm on Monday to Waterfields Retail Park in Watford to reports of concerns for the welfare of children that had been left in a car. Officers attended and the mother was located. Strong words of advice were given to the woman.'

The incident came as the UK had its hottest day of the year so far, with temperatures reaching 33.4 degrees.

The RSPCA has also seen a spike in calls from members of the public concerned about dogs left in hot cars, conservatories, sheds and caravans.

ClientEarth said air pollution is also set to reach dangerous levels, and the hottest parts of England are expected to be the North West and South East.

And forecasters have also predicted torrential downpours in parts of the country tonight, with up to two inches of rain expected in some areas.

This will bring a risk of flash flooding, with the Met Office also warning of frequent lightning, large hail and strong winds as additional hazards.

The heat has been caused by a warm plume of air from Spain and will bring temperatures close to the July record of 36.7C set only last year.