Formed of nearly 1kg of silver and standing 14in (35cm) high, 'chalice-shaped' secular cups of this type were popular for feasting in the late Middle Ages, but few have survived changing fashion or melting down for their precious metal.
Despite its secular origins, the elegant simplicity of the design - foregoing religious iconography in favour of clean lines and Gothic patterning - was perfectly suited to the post-Reformation church. It is thought that the cup was given to the church of Saint Cyriac in Lacock, Wiltshire for use as their communion cup in the 17th century by Sir Robert Baynard of Lackham Manor.
It remained in use for hundreds of years until it was loaned to the British Museum by the church in 1963.
This joint acquisition will give the British Museum greater flexibility to display the cup (which carried an insurance valuation of £1.8m in 2009 when its sale was first mooted), as well as allowing its regular display at the Wiltshire Museum in Devizes.
The Lacock Parochial Church Council, who received permission to sell the cup from a consistory court in December, needed £350,000 to complete repairs to the roof of the medieval church - the remainder of the proceeds to be placed in trust.
