The London Welsh school - Ysgol Gymraeg Llundain - was set up in the late 1950s. Much like London Welsh Rugby Club, which has been slipping down the divisions, the school is struggling because the number of Welsh families coming to the capital to work has fallen off, indeed, the flow across the Severn Bridge seems to have reversed recently.
The school has 12 children aged between four and seven. There should be a junior section but there are no pupils. However, there are 12 toddlers in the adjoining nursery school, which bodes well for the future.
Finances are precarious. Not all the parents can afford fees of Pounds 450 a term. To meet the rest of the Pounds 25,000 annual running costs requires major fund-raising efforts by parents and trustees of the school.
Sian Edwards, who has been head for six years, said: "The school plays a very important part in teaching the Welsh language when children are going back in to Welsh areas."
Parents were committed to the school and in the time she had been head only one child had left to go to an English school in London. The rest had gone back to Wales with their parents.
"It is not always an easy choice for parents who often have to make quite a few sacrifices to send their children here," she said. "Many also travel long distances across London to bring their children here. Parents like the intimacy and individual attention their children receive."
The school also provides a chance for mothers to speak Welsh. There is a high parental involvement with parents taking turns at cleaning and helping in classes.
Glynis Roberts teaches at the nursery class and has two children, Aled, aged four, and Alys, seven, at the school. She said: "The main reason I want them to speak Welsh is because I am from a Welsh-speaking family and when we go back they can speak to their relations."
She also hopes one day to return to Wales and having the language will make it easier for the children to integrate in local schools. The London school follows the Welsh national curriculum.
Mrs Roberts also thought it important that children hear their peers speaking the language as well as hearing Welsh at home . "We are proud that the language in the playground is Welsh. Even in many Welsh-medium schools back home children will often use English when out playing."
Falling rolls were a worry and there had been a push to increase awareness of the school in Wales with appearances on television in the Principality and an exhibition about the school at one year's national eisteddfod.
"The future isn't safe," Mrs Roberts said. "We do need a few more children, but the history of the school is one of fluctuating numbers.
"For a rounded education there has to be a sufficient number here to make it viable, though the school provides an excellent education."