Director of the Ashmolean Dr Alexander Sturgis said the painting was "the young Turner's most significant townscape and the greatest painting of Oxford that has ever been made". He added: "If the Ashmolean does not acquire the painting, it will be sold on the open market. All major oil paintings by Turner that have been offered at auction in recent years have been bought by foreign buyers."
The painting has been on view at the museum since 1997 where it was listed as being on loan from the Loyd Collection. The painting could now settle £3.5m of inheritance tax, a figure which is more than the tax liable on the Loyd estate which means the museum needs to raise the difference, £860,000, to acquire the work.
The museum has already secured over 90% of the funding required thanks to support from the Art Fund (£220,000), the Heritage Lottery Fund (£550,000) and Friends and Patrons of the Ashmolean (£30,000). They are now appealing for donations to raise the remaining £60,000.
The painting itself dates from 1809/10 and was the only townscape that Turner ever painted in oils, though he made over 30 watercolours of Oxford during his lifetime.
It was commissioned by Oxford printseller James Wyatt who intended to have it engraved so that he could sell it as a print at his shop at 115 High Street.
The painting shows the entrance to University College on the left, the Warden's house of All Souls College and the spire of the University Church of St Mary the Virgin on the right, and Carfax Tower in the distance.
After it was completed in March 1810, it was exhibited in Wyatt's shop and at Turner's own gallery before it was shown at the Royal Academy in 1812. In the 1830s, when Turner was choosing views of Oxford for a series of watercolours, he decided not to depict the High Street because he felt that he could not repeat the technical mastery of this earlier painting.
Stephen Deuchar, Director of the Art Fund, said: "This most important picture simply must be saved by the Ashmolean: we're pleased to have supported the campaign substantially ourselves and fervently hope that anyone else who loves Turner, Oxford and the Ashmolean, will now do the same."