Prince William joked cannabis has 'quite a good, strong smell' as he was shown into a room full of seized contraband today.

The Duke of Cambridge, 36, was left shocked at the amount of drugs and weapons intercepted by staff and border officials as he visited the Royal Mail's International Logistics Centre at Heathrow Airport.

After five minutes in the room, which was filled with packets of cannabis, MDMA and cocaine, the royal joked: 'We had better get out before we have a drugs test!'

The tour of the lock-up was part of William's visit to the centre to see the fight against the illegal wildlife trade in action.

Prince William watches as a UK Border Force officer scans via an X-Ray machine incoming mail and parcels, to the United Kingdom, for contraband goods during a visit to the Royal Mail international distribution centre near Heathrow airport

Prince William looks at an illegal animal skin seized at the centre. The tour of the lock-up was part of William's visit to the centre to see the fight against the illegal wildlife trade in action

Prince William, 36, was back to his busy schedule on Thursday, as he visited Royal Mail's Worldwide International Logistics Centre at Heathrow Airport

As he walked in Border Force officer Steve Harrington told him: 'Excuse the smell.'

The lock-up was full of packages of herbal cannabis and other drugs, as well as seized weapons and wildlife products.

'These are drugs we get here, large seizures of cannabis. It is coming from the United States, where it is legal in some states,' Mr Harrington said.

William joked: 'It's quite a good strong smell.'

Mr Harrington said the 545 drugs packages and 1,657 weapons, including stun devices and knives, had all been seized in the last month.

As he was shown the weapons, which filled one wall of the room, the duke said: 'That is a staggering amount of weapons in one month. That is quite shocking.'

Prince William smiles as he talks to Royal Mail sorting office workers during a visit to the Royal Mail international distribution centre near Heathrow airport in Slough

William watches as a UK Border Force officer scans via an X-Ray machine incoming mail and parcels

Prince William talks to Royal Mail sorting office workers during a visit to the Royal Mail international distribution centre near Heathrow airport in Slough

The centre also gets MDMA from the Netherlands, cocaine, and the occasional package of heroin from Pakistan.

Although the smell of cannabis was highly noticeable, Mr Harrington said: 'I'm fine with it. Some people don't like it. But I don't spend all day in here.'

Clive Perry, the senior manager with Border Force who showed the William around the seizures, added: 'I think my officers have got immune to it in there, to be honest. We process it and move it out as quick as we can.

'He [Prince William] did comment on it – it's something you can't ignore. I think the smell of paint in there had gone, because we had it decorated for his arrival, so the cannabis has overwhelmed it.'

Prince William watches as a UK Border Force shows off various items found recently, including snake skin, ivory and plants that are not allowed into Britain

Royal Mail staff spot suspicious packages, and Border Force officers put them through X-ray scanners. Pictured, Prince William looks at one such scanner

Prince William receives a sheet of commemorative stamps which shows the work of the Royal Mail in defeating the import of endangered wildlife and their products

Mr Perry said the centre, which just deals with packages under 2.2kg, had seized hundreds of kilos of cannabis since April. 'We get so much. The volume of stuff coming through the post is quite high.'

Cannabis and other drugs such as cocaine can be spotted by trained staff, he said. Royal Mail staff spot suspicious packages, and Border Force officers put them through X-ray scanners.

'The work we do with Royal Mail – we give them key words to look for when they are looking through the mail. They put those packets to one side, and then we would screen it and find it.

'It is all about looking at X-ray images to see what the powders look like. The prime example is just birthday cards with a dealer bag inside. It's easy to identify with an X-ray image.'

William was visiting the centre to highlight the work of the Royal Mail as a member of his United for Wildlife Taskforce which combats the illegal wildlife trade.

The father-of-three attended the site to see how they prevent the trafficking of illegal wildlife products, meeting with the team behind the operation

Meeting the team behind the organisation, William has in the past been outspoken in his passion for the industry, making wildlife campaigning one of his key charity focuses.

Prince William visits Royal Mail's Worldwide International Logistics Centre at Heathrow Airport to see how they prevent the trafficking of illegal wildlife products

He was shown four packages seized this week – two from Thailand, and two from Britain intended for China and Hong Kong.

One of the packages from Britain contained several ivory artefacts, including a pair of binoculars, and a snakeskin which is believed to have been from a rock python. 'I would not like to have met the snake that was wearing that,' said the duke. 'It is amazing what you find, it really is.'

The seized weapons he was shown included an extendable baton and a pair of knuckledusters. Mr Perry told the duke: 'The other weekend we had 500 knuckledusters in one go. Nasty weapon. We get a lot of flick knives as well.'

He was also shown the skull of an Arctic wolf, which is likely to be used as a training aid.

Weapons are held for one month and then recycled, while drugs are held for a month and then incinerated.