BLACK swan Sebastian now stands alone to incubate a solitary egg left behind by his mate, Sylvia, who is presumed stolen.

The lord and lady of Markenfield Hall have been left heart-broken after discovering one of the pair of swans roaming around the grounds had gone missing.

The black swans spent most of April painstakingly building a huge nest of twigs and feathers on the banks of the hall, near Ripon, to ensure Sylvia the female swan had a safe place to lay an egg.

However, Lady Deirdre Curteis noticed Sebastian, the male, was taking over incubation duties of a single egg left by his mate.

Lady Curteis said: “I thought it was peculiar as Sebastian – the male – always swims across when he sees anyone coming, but there was just one swan and it was sitting on the nest.”

The lady of the hall had taken to carrying jugs of grain out to Sylvia and Sebastian several times a day and began to suspect something had changed last Saturday when Sylvia was nowhere to be found.

“We searched for days, but found no trace anywhere not even a feather,” added Lady Curteis.

“Our swan man told us that it is not uncommon for thieves to take advantage of nesting birds, snatching them at their most vulnerable, but to think of it happening here – and when her egg was so close to hatching – is heart-breaking.”

Markenfield’s moat has been patrolled by a pair of black swans since Lady Curteis and the late Lord Grantley completed their phase of the hall’s restoration in the early 1980s.

The first pair of Markenfield swans were given to the estate by a friend who was the curator of birds at London Zoo – they, and their descendants, have been a constant feature ever since.

Now the search is on to find Sebastian a new mate before the Hall opens its doors to the public in May to ensure the dynasty continues.

Lady Curteis said: “He is still young, so we hope that he will accept a new female and that they will be able to live here in peace once more.”

Markenfield Hall will be open to the public from Sunday, May 5 to Sunday, May 12, and again from Sunday, May 16, to Sunday, June 30, from 2pm to 5pm.