By Jane Elliott
Health reporter, BBC News
Beryl has been a courier for three years
Beryl Sarsfield is a very special courier.
Over the last three years she has made more than 80 trips - many of these over long distances to collect or deliver bone marrow needed for leukaemia patients.
In total her trips, for the Anthony Nolan Trust, add up to three months of travelling and include visits to Australia and Canada, as well as Europe.
Beryl, a former nurse manager, admits the voluntary job can be a lonely one, but says it is great to know that her work is helping save lives.
"I feel very privileged to do it," she said.
"Because of my previous nursing knowledge I know how important this is and that it is often a last ditch treatment.
Bone marrow transplants
In 2008 The Anthony Nolan Trust got matches for 758 patients who required a bone marrow transplant
There are more than 393,000 people on the Anthony Nolan bone marrow register, but more are needed
On average, 115 UK patients in need of a bone marrow transplant are requesting Anthony Nolan Trust help in finding a match monthly and there are 16,000 search requests from patients across the world per year
"And my small part makes it happen. "
Couriers are needed to get the bone marrow cells speedily to those waiting for transplant, because although the cells can survive about 48 hours at room temperature, viability starts to decrease as soon as they are collected.
On each trip Beryl, one of 24 couriers, travels with the special carrier box, which she says has sparked a lot of interest from fellow travellers and gives her the chance to try to encourage people to enrol on the bone marrow register.
"It is like a miniature hard picnic box about a foot square, with leukaemia research and Anthony Nolan on it," said Beryl, from Stevenage, Hertfordshire.
"Because of my medical background I am absolutely fastidious about the box and don't let it touch the ground ever. It goes on my lap and if anything goes down on the floor it is my bag.
The box that Beryl takes on each trip
"Every single trip someone will see the box and ask questions about it.
"I find people want to talk about signing up and I talk quite a lot about the trust. I don't know whether anything comes of it, but I give them the website address."
Beryl has even got the support of some high-profile celebrities.
"I was flying back from Madrid and met Penelope Cruz - she was lovely.
"She was interested to talk to me about the charity and wanted to help - and did."
Responsibility of job
Beryl was one of the first couriers to be recruited for Anthony Nolan when it started using volunteers rather than staff, three years ago.
"I had just retired and within weeks of retiring I saw an advert for this in a nursing magazine. I knew very little about it and rang up to find out some more," she said.
"It is a big responsibility being a bone marrow courier, but I do not have nightmares about it.
"To start with I wanted to know whether the operation was successful, how it went, but then I realised it was none of my business."
Pauline Makoni, operations manager for Anthony Nolan, said that the courier life was definitely not for all and that although there are no formal qualifications needed, the selection process is tough.
"The couriers are responsible for getting the donations from the collection centre and delivering it in good time and in good condition," she said.
"They must make sure they collect the right product and we make all the arrangements for the transportation. They have to ensure that the product is with them at all times and that no harm comes to the product, nor that the donation is not wasted.
"We advertise for people who have time and are responsible people and then we teach them and give them trips to see whether they enjoy it and whether we feel they are reliable."
She said the expectations for couriers were very high.
"The work of a courier is very lonely. We don't permit you to travel with anybody else or deviate from our plans and we pretty much monitor you, or are at the end of a phone should you not reach point X by the time we expect," she said.
"It is actually rather stressful when you think you are caring for somebody's life.
"We treat it that this is not something we can not lose or replace. There is no element for any sort of error."