Sheep farmers had been expecting fewer lambs this season because the proportion of pregnant ewes carrying twins and triplets rather than singletons was sharply down. This dearth of multiple births is put down to particularly cold, wet weather at tupping time last autumn when the rams were brought in to mate.
The ewes may have been in poor condition at the time of conception last year or soon afterwards. Now, in the spring, their lambs are being exposed to equally vicious weather conditions.
Each year 23 million lambs are born in Britain, starting in January in the southern lowlands and ending as late as May in more northerly uplands.
Farmers estimate that they lose up to 5 per cent of lambs at birth or soon afterwards, but this year the National Farmers' Union in south-west England is making an estimate of 8 per cent.
John Thomas, a Welsh NFU official, said: 'It has been a particularly bad season - the kind that happens only 1 year in every 10 with problem after problem. A wet, cold winter has produced poor spring grass. Recently we've had torrential rain, with the new- born lambs kept outside being soaked through. They're dying from pneumonia and related diseases.'
Peter Dowling, a Cumbrian farmer with 900 upland ewes, said: 'It's the wet and cold that does for them more than anything else. A dry back and a warm sun is what they need.'
Lambing has greatly altered in the past 20 years, with scanning of embryos in the womb now becoming routine and more and more ewes giving birth in warm, dry shelters - sometimes temporarily erected in the fields and hills. But, sooner or later, the lambs and their mothers have to be put outside to make room for other ewes about to give birth.