Down House, Kent

Whereas the National Trust is popularly associated with grandeur and scones, English Heritage is more commonly associated with forts and grit.

So it is appropriate that Down House, which reopened last February after a £1m overhaul, should be run by the latter, for it was Charles Darwin's defensive redoubt, evolutionary biology's command bunker, camouflaged as an unassuming villa tucked away down a narrow lane in Kent.

It's the place where Darwin spent his most productive years and wrote On the Origin of Species, which first appeared 150 years ago this November.

Darwin's methods included co-opting members of his family into helping carry out experiments and sending out thousands of letters to men of science across the world, begging for the answer to this or that question about some minor detail.

Family members were kept in the dark about the nature of his speculations, while his scientific colleagues had no idea that their pockets had been picked for pieces to a puzzle they didn't know existed.

A slightly doddery figure in the house down the lane, the village eccentric who knitted together facts discarded by unwitting accomplices, Darwin is a very English scientist, evolution's Miss Marple.

Even today, finding the house is a challenge. I visited on one of the first fine days of spring, and neither the narrow streets of the nearby village of Downe nor the car park seemed quite able to cope with the crowds. There are cycle racks, however, and it is possible to take the bus from Bromley railway station.

Visitors to Down House collect their ticket in the shop and are first directed upstairs, where Darwin's family, his early influences and career are described in a series of relatively small and dark galleries. These include a full-scale reconstruction of his Beagle cabin, complete with young Darwin himself, shown queasily examining slides by the magic of video projection.

Architecturally the building is no great shakes, and so an installation that might seem disorientating or disrespectful in another context works well here. There are different levels of wall text, allowing visitors to skim panel summaries or read in more depth.

I was impressed by the deft way in which the Origin-or-Genesis debate was dodged. It is possible to believe in evolution as well as in a God or gods, a wall panel states, before asking why the Victorians found it so difficult.

Richard Dawkins, the evolutionary biologist and author of The God Delusion, would dub this pusillanimous, but I welcomed it. Evolution versus faith is too big a fight to pick in a genteel Kentish villa - you might break something.

Two walls upstairs feature cabinet of curiosity-style displays incorporating multiple compartments, some filled with text, others with a random selection of tat: plastic dinosaurs, light bulbs, plastic dummy volcanoes.

I assume that the intention is to relay a sense of how Darwin's collecting and reading sparked off new ways of compartmentalising knowledge. Shown in a confined space alongside reverently-displayed relics, such as Darwin's notebooks and equipment, this simply jars.

It was a relief to pass into two airy rooms with plenty of natural light; one given over to two experimenters, in period dress, and one to interactives. The latter are jauntily low-tech. A stereopticon uses primitive flip-card animation to visualise whale evolution. A pinball machine tries to get across the artificial selection involved in pigeon breeding.

This room may have an end-of-the-pier quaintness, but I had little sense that knowledge was being relayed. A large crank-operated contraption featuring bees, mice and cats seemed particularly unilluminating. More thought was needed here.

The live experiments were far more successful. Red cabbage was used to make paper that changed colour depending on its pH reading. This introduced the concept of acids, which in turn fed into an experiment in which a primitive battery was made out of copper coins, kitchen foil and lemon juice. Though neither experiment had much bearing on Victorian science or evolution, I was fascinated.

Getting off the track

In the age of the Large Hadron Collider, every room of Darwin's home is a salutary reminder that great advances in knowledge do not require great equipment. This theme is picked up in the grounds of the house, where once again you pass from one experiment to another.

Before heading outside into the sunshine, however, there are the furnished ground-floor rooms to visit. These are arranged without any labels or wall panels, as if one of the Darwin brood might bound in at any moment, or the great man himself appear from behind the screen in his study. Correspondence awaits him in a letter rack in the hall.

On entering a Victorian workhouse it was the custom to separate individuals from their partners and parents from their children. This rendered them quiet, docile and amenable to the diffusion of Useful Knowledge.

Nowadays we just make them put on headphones. Visitors to the house are lent a handheld multi-media guide containing an introduction and commentary by broadcaster and naturalist David Attenborough.

Like most people, I visit these sorts of places with friends. It's fun to drift, sharing something you find interesting one moment, being called over the next to see something you may have missed yourself, but which has caught the eye of your companion.

That pleasure is harder to come by at Down House, given the choice between headphones and pottering around the ground floor and garden with few labels to turn to for help.

The garden tour is voiced by BBC journalist Andrew Marr. Though large, the screen on my audio device became nearly unreadable in daylight. This made it hard to appreciate the visuals and video clips, but left us free to explore. Perhaps, too free. It would surely have been possible to put up three or four panels indicating how Darwin used the potting shed, vegetable patch and sandwalk to develop and test his theories.

There are fascinating tidbits available, albeit solely via the audioguide. The grounds are delightfully informal and deceptively extensive. Even on a busy Sunday afternoon it was possible to have the shady sandwalk to oneself. Darwin paced up and down it daily, trying out the pieces of the puzzle in his mind.

Without Marr to break the stillness, one could puzzle over the clues scattered about the grounds like the tell-tale bits of clothing in the Peter Greenaway film, The Draughtsman's Contract. A carefully fenced patch of bare soil gapes in an otherwise impeccable lawn.

Carnivorous plants leer through greenhouse windows. It's a very English garden, which still keeps its secrets. Thank goodness. Here's hoping that this slightly eerie sense of wonder remains when summer comes, and brings far larger crowds. Narrow lanes and a small car park can't keep them away forever, Mr Darwin.

Jonathan Conlin teaches British history at the University of Southampton