DURHAM'S Frankland top security prison has foiled an attempt to smuggle heroin to an inmate.

The drug was hidden inside a package of health food but it was discovered on Saturday by prison officers who became suspicious about the package.

The 41g of heroin is said to have a street value of £1,200 but, it is believed, could fetch around ten times more in the prison because of the difficulty in obtaining it.

A spokesman for the Prison Service said that unusual writing on the package and an incorrect address alerted officers carrying out a random mail search. The spokesman said: ''We can confirm that on April 13 a large quantity of heroin was discovered in a package for a delivery to a prisoner.

''Vigilant officers became suspicious about the package, essentially because the writing was different and it was incorrectly addressed.

''They opened the package and subsequently found a large quantity of heroin. The police were informed and are investigating.

''We are reassured that the vigilance of the staff when going about routine searching of incoming parcels has led to the discovery.''

A Durham Police spokesman said: "It was a brown powder and it has a street value of £1,200. Prison values tend to be inflated and it could be worth up to ten times that amount inside."

The Prison Service spokesman added that it was impossible to say what quantity of drugs was missed by routine checks, but the current system had been proven to be successful.

''All packages going into the prison system are subject to at least an initial look. Where there is suspicion or where we have intelligence informing us something awry is happening, we will act upon that.