Matthew Cobb

And to cut a very long story short, what we know from Crick's notes that he wrote in 1960 and from a series of interviews that he did in the middle of the 1960s with Robert Olby, who was the first historian to kind of track his work, we know that, in fact, what Watson and Crick did, they knew that the problem could be solved, but that was more because it seemed to be a simple molecule

unlike the proteins they were studying, which are horrendously complicated.

So that's what this, whatever Watson saw, it gave him the idea that it was solvable.

It was soluble.

They could do it.

And just using basic chemistry, what was already known, the chemical structure of DNA, and these very simple two-dimensional models of the components, the bases that they're called, they fiddled around.

They later said it was trial and error.

They tried anything that would fit.

They started off going back like Pauling with three strands and with the bases pointing out.

So the strands in the middle like this and then these sticky things like kind of cactus.

And that didn't work.

The chemistry didn't work.

So they went back and they tried over and over and over and over again.

And eventually they get a...

watson is that they're trying to get the bases to fit on the inside and it doesn't fit and watson literally he turns one of these bits of cardboard over so the base looks like that imagine and then the other base he's trying to get to fit to it he turns it like that

And now he can see that the four kinds of bases make two pairs.

A and T make the shape, and C and G, as they're called, make the same shape.

So now you can imagine we've got strands on the outside, and the rungs of the ladder are always the same size.

Now, when they saw that,

What Crick said was that it fitted with some evidence from Franklin that they had been shown by their boss, Max Perutz.