They survived the iconoclasm of Henry VIII and the English civil war, but beautiful examples of early religious art in churches are now under threat from neglect and even heating, experts warned Wednesday.
The painted rood screens - the stone or wooden structures that divide the public part of a church from the priest's area - depict saints, prophets and kings and some are viewed as masterpieces of medieval art.
Many were destroyed in religious violence in the 16th and 17th centuries because they were associated with the pope and the Catholic Church after the Reformation.
But of the several thousand that survived in parish churches in Britain many are now threatened by insect attacks, damaged by bat faeces or warped by fluctuations in temperature and humidity caused by central heating.
"This is a cause for national concern," said Catherine Cullis, churches officer from the Society for the Protection of Ancient Buildings, which has raised the issue in its membership magazine, "Cornerstone".
"Wonderful painted rood screens are among the surviving glories of early English art, but their future has been compromised as much by our complicated religious history as by lack of protection.
"It seems that many rood screens survived the violent iconoclasm of the Reformation, only to fall victim to benign neglect in the 21st century. Elsewhere they would surely be valued as medieval masterpieces and treated accordingly."
In Old English, "rood" means cross or crucifix.
Cullis acknowledged, however, that with church attendance and funding dwindling, most congregations were preoccupied with keeping their buildings watertight.
Many also did not understand that "even something such as turning up the central heating can cause a problem", a spokeswoman told AFP.
A survey by the National Churches Trust in April found eight percent of 47,000 churches, chapels and meeting houses in Britain were in poor or very poor condition.