I'm trailing in the wake of a tall and striking blonde woman who is stopping men in a busy street asking them if they've thought about having children, and if they'd consider donating their sperm. Most seem a little surprised initially, but they are willing to listen and she hands them one of her glow-in-the-dark sperm-shaped key rings labelled "Very Special Man", before heading off in search of the next likely candidate.
She's Laura Witjens and I've been following her on and off for the last six months, making a documentary for BBC Radio 4 about the setting up of the world's first National Sperm Bank which she heads. Her approach to recruiting sperm donors may be somewhat unusual, but it's part of a drive to encourage more men to at least think about donating.
For some couples who long for a baby, and for many single women and lesbian couples, donor sperm is the only way they will be able to conceive - but when they visit their local fertility clinic, they may find that they are advised to consider using sperm imported from donors in the United States or Denmark. We've been relying on imports of donor sperm to help meet demand, and there are disadvantages to this. In the UK, we have a limit of ten families for each donor but there are no national limits for overseas donors. Children whose parents have used imported sperm may be one of many dozens of half-siblings across the globe.
So why don't more men here in the UK donate? It's something I've discussed with Laura, who is Dutch and very open about such matters. Could it be embarrassment, a natural reticence in our national character or is it more to do with a lack of awareness and encouragement? Many fertility clinics in the UK simply don't have the time or resources to devote to recruiting and retaining donors. For every 20 men who express an interest in donation, only one will prove to be suitable - they don't just have to have top quality sperm, they also have to be screened for infections and diseases, and then have to commit to regular visits to donate. Perhaps it's not surprising that many clinics in the UK find it simpler to buy in sperm from overseas.
I began following the story of the National Sperm Bank from the very start, when the Department of Health awarded a grant to set it up last summer. Laura had decided Birmingham was the ideal location, and had begun working with Dr Sue Avery at the city's Women's Hospital where they already had a local sperm bank.
Laura and Sue hope to capitalise on Brummie pride to encourage men to consider donation, and aim to reverse the trend of using overseas donors. Birmingham's central location and ethnic mix make it an ideal spot, as shortages of sperm from ethnic minority donors are particularly acute. Laura has already been out with community leaders and the team are working on local campaigns over the summer to get more men to sign up.
Another reason Laura cites for choosing Birmingham is the city's proud manufacturing history, and on one of my visits to the bank I met up with historian Dr Chris Upton who told me that this heritage is part of the city's DNA. For him, the fact that the first national sperm bank is located in Birmingham is a positive story; "We are still manufacturing something in the 21st century," he said, "something rather different to buttons and buckles!"
The initial publicity for the bank brought a flurry of enquiries, but in reality not everyone who gets in touch will end up being a donor. Some may not be suitable, others may not be willing to make the commitment and although a few men are now regularly donating to the national bank, many more donors are needed if it is to become a success. I get to meet a couple of the men who donate regularly, and they both express their pride at being a part of the project saying that they would encourage others to consider donating.
As I pay my final visit, I realise that getting a proper national bank in place is going to take time - but with the determination of the team and their belief in the men of Birmingham, they may just do it!
Banking on Birmingham: The National Sperm Bank will be broadcast on BBC Radio 4 on Monday 22 June at 11 am