We left Denham in the by-now familiar Western Australia weather of sun, blue sky and strong winds. We planned on a fairly short day's drive, just taking in a few sights of the Shark Bay national park along the way.

First up was Eagle Bluff, not far to the south. This was a vantage point high above the sea from where you were meant to be able to see sharks, rays and turtles in the water below. Unfortunately the tide was out a fair way which meant we glimpsed none of these creatures and with the wind whipping in off the ocean we beat a hasty retreat to the car.

Next was Shell Beach, a brilliant white expanse not of sand, but as you can easily guess from the name, shells. These all come from a type of cockle which thrives in the salty water of the bay. When they die, their shells are washed ashore and form the beach, which in places is up to 10 metres thick.

This was a reasonably picturesque spot, but having spent about 10 minutes on the beach looking at its whiteness and taking a few photos we decided there was no reason to linger.

Third and potentially most interesting of our planned sights was the stromatolites at Hamelin Pools. "What on earth are stromatolites?" I can hear most of you asking. Well, they are rocky structures created by the trapping of sediment by micro-organisms called cyanobacteria. The reason they are significant is that the cyanobacteria are virtually identical to the first life forms to evolve on this planet. This was around 3.5 billion years ago and they "ruled the earth" for the next 2.5 billion years or so.

Ironically, their very success eventually led to their undoing. One of the things cyanobacteria do is produce oxygen and over time the countless zillions of them produced enough oxygen for more sophisticated life forms to evolve and eventually take over. Marine stromatolites now exist in only a couple of places in the world - one in the Bahamas and one in this very salty southern end of Shark Bay.

I'd read Bill Bryson's account of his visit here and how stromatolites are in fact very dull. Well, they are just bits of rock really. But with nothing much else to do we decided to make the small detour to see a bit of very ancient history.

At first we wondered why we had bothered. Access was only through a caravan park, which contained a small museum apparently containing a stromatolite in a tank though most displays were devoted to a now-defunct telegraph station. It was closed, however, so we headed over to the information area cum tearoom cum shop. There we found copies of the relevant page in Bryson's book, but not much else. Interestingly, there were no signs saying "Stromatolites This Way" or anything so useful. Instead, everything pointed to the commercial activities of the site.

Eventually we found a map board indicating where the stromatolites were and headed off to a boardwalk to have a look. And I have to admit we were both surprised at how interesting these funny little things were.

We had in fact seen the stromatolites on our initial drive in the opposite direction. We had seen some black stuff in the distance on the beach and wondered if it was pollution or seaweed. No, it was just the stromatolites, poking up darkly through the low tide.

The boardwalk information signs helpfully showed us the different types of stromatolite, which ranged from flat black "mats" to stumpy little "club" shapes. There were also some with reddish tops - probably a result of iron being somewhere nearby.

Although they didn't "do" anything and neither were they spectacular, it struck us that we owed these funny little rocks and the cyanobacteria some thanks - if they hadn't been huffing and puffing away for billions of years producing a small amount of oxygen each, then none of us would exist.

Feeling suitably philosophical, we drove off to our planned stop at the Overlander roadhouse just a few km away. When we arrived there, however, we found that the "camping area" was just a nasty patch of red earth. Given that we would have to pay $20 for the privilege, we decided to drive on. Unfortunately the next roadhouse had a proper motel attached but no proper camping area.

By now time was pressing and the only other options were to drive on to Kalbarri, which was a long way, or risk one of the free "rest areas" listed in one of our guide books. Many people swear by these stops because of the lack of cost, but having pulled up at a few we never really fancied them. If we were in a van it would be different - for one thing you could lock your doors and pretend you were on a proper campsite. But camping in a small tent pitched outside a public toilet just doesn't have much appeal, does it? And that brings up the ultimate disincentive - the quality of the toilets. Most are "long drop" and look and smell as if no-one has cleaned them for a couple of weeks.

In the end, we decided to check out the rest area at Nerren Nerren and were encouraged to see around 15 caravans and cars already parked there. We drove around and found that while most of the surface was gravel there were areas of red soil where we could pitch a tent.

More importantly the final "nose test" proved satisfactory - though only just! Katy went just the once and claims to have held her nose for the entire time, fastening up her clothes with one hand apparently.

We erected our tent with only a little difficulty in the hard soil and started to cook our very simple campers' dinner. That was when the flies started to gather. It was like that scene in The Birds when the feathered creatures congregate outside the school. We knew there were a lot of flies around, but it was only when I opened a tin of tuna and tried to serve it up with our potatoes and baked beans that the flies attacked. Suddenly, there were hundreds of them all trying to get a piece of us or our food. It was utterly vile.

We practically threw the food onto our plates and immediately jumped into the car. We ate our sumptuous repast in the front seats as the sun went down. Hardly a glowing recommendation for free rest areas, I'm sure you would agree.

Richard