POLICE have issued a warning as door-to-door sellers - also known as Nottingham Knockers - were seen operating in villages across Test Valley last week.

Officers are warning residents to be vigilant and to read the following advice so that they are prepared to deal with such callers:

• Always use the door chain when answering the door, if you are not sure do not open the door.

• Always check the credentials of unknown callers. Do not phone the number on the ID card, use a phone book or a bill.

• Never buy from cold-calling doorstep traders or engage with cold callers on the phone.

• Do not keep substantial sums of money in the home.

• Always keep front and back doors locked.

• LOCK STOP CHAIN and CHECK - if unsure do not open the door.

• Consider joining or setting up a No Cold Calling Zone or Neighbourhood Watch scheme.

• Report any suspicious callers or activity to the police immediately.

• Keep an eye on elderly or vulnerable neighbours, friends and family.

• Call 101 to advise of any unexpected callers - this gives police a better chance at building a picture of where potential criminals are operating.

These callers tend to be selling cleaning materials and are usually male, from the north of England and carry large black holdalls.

Dubbed 'Nottingham Knockers', they may claim to be ex-convicts attempting to mend their ways but they will not be under any recognised rehabilitation scheme.

They may also show a card purporting to be a permit under a rehabilitation programme but the Probation Service does not run such schemes.

The 'traders' will be supplied with a bag of household products e.g. tea towels, dusters, gardening gloves, for which they are charged a minimal amount by their 'employer'- originally a man from Nottingham, hence the name.

They can keep whatever they make above the amount paid.

Often known criminals, they will be deposited in a transit van and told to work a certain list of streets then they will be picked up and taken to another location.

The products - which are usually poor quality - will come to the price of a note and when the householder hand the cash over they will assess the address.

If it is crumpled they accept it and move on but if it is a new note they are likely to engage the resident in further conversation to glean information and when they leave they will smell the note to assess whether there is more in the property.

If it smells slightly musty it is an indication of more.

A list of addresses will be given to the 'employer' which can then be sold in prisons and pubs and passed onto rogue traders.

If you encounter any such callers, contact Hampshire Police on 101.