“How do hedgehogs mate?” asked David Attenborough on his mammal TV programme the other night. “The answer is very gently.” The great zoologist might equally well have been talking about the coupling of his two local colleges in Richmond upon Thames.

The courtship of Richmond Adult Community College and Richmond upon Thames Tertiary College, encouraged by the South London Learning and Skills Council, turned prickly and before long the tertiary college principal Eric Kirby resigned. His successor was due to be appointed this week.

Battle lines were drawn across the railway tracks near Twickenham rugby ground after adult college principal Christina Conroy set up a centre for part-time study for 16 to 18-year-olds - a clear breach of local treaties. The tertiary college hit back by setting up its own centre the other side of the tracks. Now the adult college is setting up a business school.

But a fortnight ago both sides declared a truce and are considering a merger again. It seems they may now have a common enemy.

The Conservatives, who took control of the council in May, want to set up sixth forms in all eight 11 - 16 schools, a clear threat to the tertiary college that now takes them.

Education cabinet member Geoffrey Samuel said: “We do not want a two-tier system of schools with sixth forms and others who don’t have them. So we are putting together a consortium of schools and colleges to run franchised sixth forms in all the schools.”

The South London LSC, however, fears massive duplication of courses and resources. It ordered an area review that proved there is little current duplication of sixth-form courses with only a single Catholic school duplicating what is on offer at the tertiary college.

Richmond Tories’ aim is familiar: to increase diversity and choiceof providers. But Vic Seddon, executive director of the local LSC says there are “simply not enough resources to go round” for every school and college to set up their own sixth form.

The best solution, he suggests, is for all providers to agree a partner ship that would let the tertiary college run courses in schools. If the two colleges merged, such collaboration would be easier.

Ms Conroy said the adult college agrees“in principle” with Mr Seddon. “Richmond post-16 education is in a mess,” she said. However she wants an independent steering group set up to look at Richmond restructuring, chaired by a “person of repute”.

But a surprise intervention from the minister for London schools Stephen Twigg has caused alarm in both colleges. In a letter to Mr Samuel this week the minister expressed support for the Conservative proposal to set up a 14-19 consortium. Crucially this would run libraries, community and vocational provision on school sites. He has invited the college to pioneer it as a “pathfinder” 14-19 project backed by the Department for Education and Skills “It is very encouraging,” said Mr Samuel.

The adult and community college has twigged that such a pathfinder project is a threat to it too. It would also suggest the Government has given up the idea of tertiary colleges. The truce is the first stage in a fight by both colleges to hang on to their roles.