A rhino head that a gang thieves attempted to steal from Norwich Castle is close to making a return – with its valuable double-horn removed.

Staff foiled attempts to lift the 19th century African black rhino head, valued at up to �500,000 on the black market, out of the museum in February.

But the horns, said to have a higher street value than gold, have now been removed during six months of restoration work.

They have been replaced with replicas moulded from the originals, while damage to the rhino's left ear, lip and chin and has also been rectified.

The word 'replica' is also clearly displayed on the rhino's new double horn in an attempt to deter thieves, with similar raids happening across Europe and in Ipswich.

No date has been fixed for the exhibit's return but it is hoped it will be back on display in early November.

Dr David Waterhouse, who has been carrying out the restoration in his spare moments at work, said it had been a 'pain-staking process' and he needed to be very careful removing the original horns, which had been nailed in position for more than 100 years.

Norfolk museums service's curator of natural history said: 'That's what saved it when the attempted theft took place. They were nailed in with 100-year-old nails.

'They were difficult to get off – that was quite a long process to remove them without causing any further damage.

'Once the horn was off and cleaned it was put in a safe. But we made the replica of the real horns. They are identical – apart from the big word 'replica' written on them.'

Currently, a miniature model version of the rhino sold to tourists is on display in the head's place, with a note explaining the attempted theft.

Dr Waterhouse said: 'It's an early 19th century African black rhino that came to us when it was a popular, or relatively popular and accepted thing, to shoot things and get the heads. It was displayed as a trophy for years and years and we didn't really shy away from that.

'That was what was done, We felt it was important to get across the conservation [of rhinos] message and we have conservation action points in the gallery now so people can learn.'

Barry Stone, county council cabinet member for cultural services, said he is excited the rhino head is almost ready to return and has been restored to its 'former glory'.

He said: 'Due to the expert knowledge of staff at the museum the artefact has been sympathetically restored and it has been made to look as natural as possible.

'We very much hope that when the rhino head is back on display it will once again be a popular attraction for the people of Norfolk, as well as for those from all over the country visiting the castle museum.'

Nihad Mahmod, of no fixed address, was jailed for two-and-a-half years for the attempted theft of the rhino head in July. Patrick Kiely, of Eleanor Street, Bow, in East London, has been charged and is awaiting trial in connection with the incident.