'Bogs oaks' reveal ancient forest

Fossilised trees in Wales have proved useful to scientists

The remnants of ancient forests that once covered Britain are being revealed in fields across the Fens.

Conservationists say dozens of the "bog oaks" - which can be up to 40ft (12m) long - have been unearthed.

The remains of a forest that existed after the ice age, the trees rotted and fell into the peat soil, providing a snapshot of ancient natural history.

Conservationists say more may be discovered as the Fenland peat is drying out and oxidising.

The peat is believed to be disappearing at the rate of about an inch a year.

Although the trees are known by the local name of bog oaks, they can also be yew or pine.

BBC environment correspondent Sarah Mukherjee said they look as though they have just been felled - although some are blue or dark red from the minerals they have absorbed.