While the old image has not exactly been given the brush off there have been changes. There is a move towards establishing chimney sweeping as a craft skill, embracing new technology but keeping tried-and-tested methods and cherishing at least some elements of the folksy image.

“To a large extent sweeps are still regarded as loveable cockney rogues,” says David Gough, of the National Association of Chimney Sweeps. “Dick Van Dyke did us no favours. And The Water Babies. I go to some houses in the school holidays and mums will say - do you chaps still use children? You can take this lot for nothing.”

In Europe the chimney sweep is greatly respected. In Scandinavian countries sweeps have the power to inspect chimneys and shut them down, while in Germany they have more authority than English building inspectors.

English sweeps would like their considerable and growing expertise to be recognised in a consulting role, advising builders, council inspectors and insurance companies. They also want a national registration scheme.

The National Association of Chimney Sweeps has its own training centre at Stone, Staffordshire, and offers a two-day induction course for people who are considering becoming sweeps.

They start the day covering health and safety. For instance, our grandfathers may have told us that soot is good for the allotment but in fact it is carcinogenic. The second day is devoted to cleaning techniques and opportunities to talk to experienced sweeps. A classroom at the training centre has examples of domestic heaters and boilers and the chimneys and flues they require.

The danger of carbon monoxide poisoning is stressed repeatedly. Vents have to be sited properly and a simple thing like a spider’s web can block the flue from a domestic gas boiler.

“We give people on the course an attendance certificate. It’s by no means a qualification and we emphasise that,” explained David Gough. “Chimney sweeping is a craft skill and it does take a considerable amount of time to learn.”

Sweeps are encouraged to train for qualifications from the different fuel associations. When they have them all they can call themselves a master chimney sweep.

There is now a national vocational qualification in chimney engineering and the training centre at Stone acts as an assessment centre.

Martin Glynn, president of the national association, was the first sweep to gain an NVQ and a 20 per cent free discount has been negotiated for members.

Clearly the association would like to see every chimney sweep with an NVQ but that will take time. In the meantime sweeps will be encouraged to attempt the clean flues and appliances unit.

Employment prospects are good. David Gough insists that he knows of chimney sweeps who make a good living from attending weddings and not bothering to clean a single chimney, but for the serious sweep there is plenty of work.

Fireplace and stove suppliers want a qualified sweep on their permanent staff to prepare a chimney prior to installation. Many insurance companies will not insure a home unless the householder has the NACS certificate of sweeping, so many more flues and chimneys are being swept. And not just those with a fire - unused chimneys attract dust, cobwebs and crisp packets and they need an annual cleaning.

“People are expecting us to have a broad range of knowledge - it’s no longer a 10-minute job”, said David Gough. “The sooty face is just for the weddings.”

“It really is an interesting job”, says Martin Glynn. “No two days are the same, no two chimneys are the same.

“I have security clearance to clean chimneys in Whitehall. Those government offices change, the fronts of the buildings change but not the chimneys. They’re just as they were in Georgian and Victorian times - beautiful. It’s a different world up there on the rooftops of London.”

I half expected him to burst into song, but we’ll leave that to Dick Van Dyke.