'Would youlike some run-backs?'

'We can try.'

He told the girl and the scene began swinging anti-clockwise at precise intervals with five-second stops. It didn't make any difference: I was looking at the same thing in a mirror. There's no point in run-backs unless you think you've spotted something and want to recap and I hadn't spotted a bloody thing and I was getting fed-up. The heat of the projector was adding to the heat of our bodies in here and there was nothing much left to breathe and I thought it'd be nice if a girl came round with a tray of Dairymaid.

The dunes flowed under my eyes.

Swing. Stop. Run-back.

The projector droned.

I kept wanting to look at the rocks but Eastlake had said it wasn't worth bothering with. They weren't interested in the rocks. And it was no good asking them for a clue because the object of the exercise was that I should see the target for myself, avoiding the risk of conditioned illusion.

Swing. Stop. Run-back.

The dunes were becoming a mirage. The dunes and the rocks and the flow of light and shade across the scene were beginning to swirl in a slow-moving vortex and I was losing track of perspective.

'Would you like us to back-project against a — '

'What? No. Run it back. Run it back, will you?'

The scene swung to a stop.

'Tell me when — '

'Yes.'

Anti-clockwise. The shadows flowing and the angle. Stop.'

'This frame?'

'Back another fraction.'

The sprockets whirred again and stopped. 'Yes, that's the one. I've got it now.'

'It didn't take you long.'

'You're joking.'

The WRAF shut down the projector and we all stretched our legs.

'It took us a bit of time ourselves,' said Eastlake, 'even though the navigator had seen it through direct binocular vision.' He showed me a couple of dozen stills and blow-ups and filter-screen montages on the static viewers but they weren't any clearer, and even the still they'd taken from the frame of the movie strip didn't have the same definition. I asked Johnson about that. He was the interpretation officer.

'It doesn't seem possible,' he said, 'does it? When you look at the still you're looking at exactly the same picture as the one on the strip — but there's some data missing, all the same. The eye hasn't got anything for immediate comparison. It's the movement through the projector that leads the eye over the changing pattern till it suddenly sees an inconsistency. That's what happened with you.'

Eastlake cut the viewer lamp and someone pulled the curtains and stopped sharp when I said: 'What sort of plane is it?'

Someone gave a nervous cough.

Squadron-leader Eastlake said: 'Don't you know?'

'If I did, I wouldn't ask.'

It was perfectly all right if the Bureau had its reasons for pitching me in here without any briefing, but if their idea was to get me steamed-up about this thing then people would haveto answer the questions I wanted to ask them or it was go.

'Thank you, Phyllis. That's all we needed to see.'

When the WRAF went out and shut the door the pilot and navigator and photo-interpretation bod stood looking at their toes and Eastlake said:

'Mr Gage has been fully screened.'

They relaxed a bit and one of them offered a package of gum around and nobody wanted any and the pilot said: 'We were told to look for a medium freighter.'

'You think this is a medium freighter?'

We were grouped by the static viewer. On the blown-up still it didn't really look like an aeroplane at all but now that I'd seen it on the movie strip I could accept the smudgy configuration on the sand as an aircraft with one wing dislocated at the root end.

The interpretation officer didn't say anything. The navigator shrugged.

'All I'd say from the pix is that it could be. From what I through the binocs I'd say it's not military and not very big.If I had a bet on it I'd put it down as a light or medium twin-prop short-haul commercial transport.'

'Not just because that's what you were told to look for and expected to see.'

He smiled lopsidedly. 'What can we ever do about that? Once we're told what kind of target to look for, we're to an extent conditioned.'

I was feeling it difficult now to look away from the static viewer. In the illuminated central frame the picture wasn't verybig: it had been blown up to the point where the grain would start blurring the definition. The ribbed background of dunes was perfectly clear but the grey ashy smudge could be anything — or nothing, just a fault in the processing — but even from sixty-five thousand feet they'd seen it was some kind of aircraft and now that they'd found it the Bureau bad cabled Tokyo fully urgent and I was here looking at this vague configuration on the photographic plate that was the focal point of the mission they were trying to sell me.

'Where is it?'

Eastlake spoke before the others could start worrying. The people with No. 2 Fighter-Reconnaissance Squadron RAF spent most of their time taking the sort of pictures that nobody really wanted to reprint as post-cards for the tourist trade. This was one of them.

'Longitude 8°3′ East by Latitude 30°4′ North.'

' Tunisia?'

' Algeria.'

'When did the plane come down?'

'We weren't informed. Our job was to look for it and take pictures if we found it.'

'From sixty-five thousand feet?'

'It's the highest we go.'

'You could've gone lower.'

Someone coughed again.

I thought I might as well push them right up against the wall so that they'd either have to answer my question or throw me out.

'Did you get official overflying permission?' I counted up to seven.

'Did we what?'

Very slowly I said: 'Did you get official permission from the Algerian government to overfly their territory and take those pictures? Or did you go up to the maximum operational ceiling because the view was better?'

This time I was at nine before the pilot said:

'Actually, neither.'

It was just their natural disinclination as secret reconnaissance men to trust an unknown civilian with the whole score. Eastlake had told them I'd been screened and they'd obviously been briefed to give me all the info they could, but they still didn't like it.

I suppose the pilot thought that if things had gone this far it couldn't do any harm to go the whole way and the squadron leader would slap him down in any case if he made a mistake.

'You see,' he said with a perfectly straight face, 'we were tooling around in Malta on a friendly visit and then we got these orders from on high. So we planned a suitable exercise and went in at our best altitude so we wouldn't annoy the scheduled airlines. Then we sort of lost our way a bit and after we'd got back on course for home we found Charlie here had made a silly mistake and left all the cameras running. I really don't know what things are coming to, in this mob.'

The squadron-leader was looking out of the window. He didn't say anything.

'You must have been tracked by radar.'

'Bound to have been.'

'How long were you overflying Algerian territory?'

'Not long enough to sort of cause too much comment.'

'Did they put up interceptors?'

'Don't actually know. You see, from that height we can go rather fast in quite a short time, by pointing things downwards.'

It was all I wanted to know and I left it at that.

When Eastlake took me down the corridor he said: 'Where exactly do you fit in with this little circus?'

'You can't see much from those photographs. I suppose they'll send me in to have a closer look at the bloody thing.'

Therewas nobody around in Field Briefing so Tilson sat me downand folded his chubby hands and said: