London, United Kingdom —A spate of thefts targeting the bright red post boxes that have been a feature of Britain's street corners since the 19th century have forced the postal service to fight back -- with an arsenal of hi-tech tools.

Royal Mail has unveiled plans to use forensic tagging to identify stolen post boxes and even electronic tracking to keep a close watch on these reassuringly iconic landmarks of winding lanes and village greens.

The company has warned of "a significant threat" to the boxes -- particularly in "isolated rural localities" -- and is teaming up with the public body Historic England to protect the 115,500-strong network.

The Letter Box Study Group -- an association of enthusiasts that has become the authority on the history of the British roadside letter box –- estimates that up to 200 boxes are pinched every year.

Royal Mail puts the figure at around 100 on average.

Some of the more flagrant cases this year include four valuable Victorian-era post boxes swiped over just one weekend in January in three Norfolk villages in eastern England.

Photos published in a regional newspaper showed one post box in Nunthorpe in northeast England had been crudely ripped away from the brickwork it was mounted on, leaving a sorry pile of rubble.

- 'Part of the national image' - 

But Royal Mail has a strategy to tackle the letter box bandits.

"We have an internal security team at Royal Mail looking at equipment, including forensic tags, permanent metal-marking systems and electronic tracking," a spokeswoman told AFP.

"Theft of post boxes is relatively rare but there are spates involving individuals or gangs."

Robert Cole of the Letter Box Study Group said thieves were likely to have three major motivating factors.

"There are people who are after scrap metal, those who are interested in the contents and those who know the boxes' heritage value," Cole told AFP.

Along with rising metal prices, one theory behind the crimes is that when Royal Mail stopped auctioning off its old boxes in 2003 it reduced supply and thereby bumped up prices.

A search on a popular online auction site showed the prices people are willing to pay for more unusual Royal Mail boxes -- one pillar box was being offered for £5,775 ($8,995), another at £5,200 ($8,091).

Post boxes vary hugely in size, shape and rarity.

The Letter Box Study Group has identified around 800 different types of box across the country, including the "Liverpool Special" pillar box dating from 1863 -- one of only seven ever made.

Introduced in Britain by novelist and General Post Office official Anthony Trollope (1815-1882) following a reform in 1840, the locked roadside boxes are traceable to mid-17th century France.

They usually carry the insignia of the monarch reigning at the time of their placement.

There is a now a post box within half a mile of over 98 percent of the UK population -- a legal requirement that Royal Mail has to stick to as the country's universal postal service provider.

In its rallying call for post box preservation, Royal Mail said it hoped to conserve the legacy of objects that "are so highly regarded that they have become part of the national image".