ARRESTS for crimes involving so-called legal highs has dropped significantly since a new law was introduced two years ago.

May 2016 saw the introduction of the Psychoactive Substances Act, making the sale and possession of a range of substances illegal after many were sold over the counter in Head Shops or online to anyone aged over 18.

According to information obtained through a Freedom of Information request, West Yorkshire Police made 19 arrests under the act between May 2016 and December 2016 for either possessing or supplying the substances and gases, which included Spice and Nitrus Oxide, also known as Hippy Crack.

The number of arrests dropped to 17 in the following 12 months and so far this year only four people have been arrested, highlighting a breakthrough for police and the Government, who regularly warned how dangerous the drugs could be.

A Telegraph & Argus investigation back in 2015 revealed how the substances were as easy to get hold of as a packet of sweets.

We told Dominic Segrave's story - a man who said Spice turned him into a shameless thief who stole from family, friends and a charity that gave him shelter.

He became homeless after he quit his job at a casino and struggled to get on with family,

He ended up being thrown out of the tiny one-bed home he was sharing with his mum in Little Horton and started buying Spice from shops in Bradford.

Mark Burns-Williamson, West Yorkshire’s Police and Crime Commissioner, said: “I was pleased when the Psychoactive Substances Act was introduced in 2016 as I had called for existing laws to be tightened up to reflect the sale of such substances.

“That legislation made it illegal to produce, supply, offer to supply, possess with intent to supply, import or export psychoactive substances.

“It also targeted those who sell these potentially lethal substances and provided the police with greater powers to take action against those who produce or supply them. Then amendments to the Misuse of Drugs Act in December 2016 further strengthened legislation to ensure those in possession of these drugs can be prosecuted.

“Combined with this legislation is really effective partnership working and awareness raising campaigns by West Yorkshire Police and partners which have meant that retailers and others know of the human impact and their moral responsibility to stop selling these drugs.

"People increasingly know and recognise the effects of these substances and it is testament to our partnerships and innovative working that West Yorkshire Police have been praised for helping keep more of these substances off our streets keeping communities safe and feeling safe.”

A spokesman for West Yorkshire Police said: "Psychoactive substances mimic the effects of controlled drugs such as Cocaine, Ecstasy and Cannabis, are commonly used as alternatives and have similar damaging effects.

"Operation Nightshot is a West Yorkshire Police Organised Crime Operation focusing Psychoactive Substances and their use, with a view to decrease the amount of hospitalised casualties and improve public confidence and awareness.