Mrs Hartley has had a harvesting operation for her eldest son

Allison Hartley was found to be a match for 12-year-old Joshua, who has the rare degenerative condition XLP.

Joshua, from Romsey, Hampshire, has undergone days of chemotherapy at London's Great Ormond Street Hospital.

Mrs Hartley has undergone the 'harvesting' procedure, with Josh due to have the transplant transfusion itself on Wednesday or Thursday.

Mrs Hartley underwent what is known as a Peripheral Blood Stem Cell Collection (PBSC).

Joshua, 12, made his own TV appeal for bone marrow donors

Her husband, David, said: "Josh is now well into his second week at Great Ormond Street.

"He is tolerating the chemo very well at the moment with only some temperature spikes early evening.

"He remains in good spirits and is very pleased that dad has brought his laptop in."

He thanked all those who have offered support to the family.

More donors needed

A spokeswoman for The Anthony Nolan Trust, which is still appealing for more bone marrow donors aged between 18 and 40, said: "Having the chemo has been tough for him and being in isolation from his noisy brothers.

"But, he's received hundreds of cards from people he doesn't know. That's what's kept him going."

The four boys - Joshua, Nathan, 10, Daniel, eight, and Luke, four - were diagnosed with the extremely rare genetic defect known as X-Linked Lymphoproliferative Syndrome, or Duncan's Syndrome, in November.

Doctors say the only cure for the boys, who are among just 100 people to have the disease, is the bone marrow transplant.

A potential donor has been found for Daniel but matches are still required for Nathan and Luke.