Sheffield tree campaigners could take their fight to save a rare elm from the chainsaw to court.
The city council has decided to fell the 120-year-old Huntingdon elm on the corner of Chelsea Road and Union Road in Nether Edge, despite repeated pleas for it to be retained.
It is home to a colony of rare white-letter hairstreak butterflies, and is one of few across the country to survive an outbreak of Dutch elm disease.
The authority says the tree's roots are growing underneath the road and causing 'irreparable' damage to the pavement, so it needs to be replaced.
Cabinet member for the environment Bryan Lodge has previously said keeping the tree and re-engineering the highway would cost £50,000.
This was despite the independent tree panel, set up to advise the council, suggesting it was a 'notable and rare species' and should not be felled.
Tree campaigners say they have been told the road work could be done for less than £3,500. They argue the elm just needs 'routine' maintenance in order to survive.
And this week members of Sheffield Tree Action Groups, or Stag, have promised to pursue legal action if the council does not change its mind.
The group says its solicitors have advised there are good grounds for a judicial review.
Campaigner Richard Ward said: “We desperately do not want to go down the litigation route.
"However the council decision to fell such an important tree is clearly flawed and incorrect based upon the facts available."
Mr Ward said the group had 'pleaded' with the council and offered to meet and come up with a 'sensible brokered solution'.
But campaigners are now worried the tree is due to come down in the coming weeks.
The council and Amey plan to fell and replace 6,000 of the city’s 36,000 street trees by the end of the year under the Streets Ahead PFI contract, while planting an extra 600.
The authority says those 6,000 are either dead, dying, diseased or dangerous, or causing damage to the highway.
But campaigners believe no healthy trees should be felled.
Judge Andrew Saffman is expected to decide in the next week whether or not to grant an injunction against three campaigners - Dave Dillner, Coun Alison Teal and Calvin Payne - who the council say are protesting 'unlawfully' by entering safety barriers put up around trees that are due to be cut down.
The council is also bringing proceedings against 'persons unknown'.