'We were honoured to have you as our guest, ma'am,' he said, delivering the one sentence he had rehearsed.

'And I have to agree with you, Mr President, when you said that your beef is the equal of anything we can produce in the Highlands of Scotland.'

They both laughed, although the president wasn't sure why.

The ambassador glanced over the president's shoulder, checking that the prime minister, the mayor and Mr Martinez were all planted in their correct positions. He noticed that Martinez couldn't take his eyes off the princess. He gave Becky a nod, and she immediately stepped forward, took her place behind Sebastian, and whispered, 'Mr Clifton?'

He swung round. 'Yes?' he said, surprised anyone knew his name.

'I'm the ambassador's private secretary. He has asked if you would be kind enough to come with me.'

'Shall I let Don Pedro know?'

'No,' said Becky firmly. 'This will only take a few minutes.'

Sebastian looked uncertain, but followed her as she weaved her way through the chattering crowd of morning suits and cocktail dresses, and entered the embassy by a side door that was being held open for her. The ambassador smiled, pleased that the first part of the operation had gone so smoothly.

'I will indeed pass on your best wishes to Her Majesty,' said the princess, before the ambassador guided her across to the prime minister. Although he tried to concentrate on every word the princess was saying in case anything needed to be followed up, he allowed himself the occasional glance in the direction of his study window, in the hope of spotting Becky coming back out on to the terrace, which would be the sign that the meeting between father and son had taken place.

When he felt that the princess had had quite enough of the prime minister, he moved her on to the mayor.

'How nice to meet you,' said the princess. 'Only last week, the Lord Mayor of London was telling me how much he'd enjoyed visiting your city.'

'Thank you, ma'am,' the mayor replied. 'I am looking forward to returning the compliment some time next year.'

The ambassador glanced in the direction of his study, but there was still no sign of Becky.

The princess didn't last long with the mayor, and discreetly made it clear that she wanted to move on. The ambassador reluctantly fell in with her wishes.

'And may I be allowed, ma'am, to present one of the city's leading bankers, Don Pedro Martinez, who I am sure you will be interested to know spends the season at his home in London every year.'

'This is indeed a great honour, Your Majesty,' said Martinez, bowing low, before the princess had a chance to speak.

'Where is your home in London?' enquired the princess.

'Eaton Square, Your Majesty.'

'How very nice. I have a lot of friends who live in that part of town.'

'If that's the case, Your Majesty, perhaps you'd like to join me for dinner one night. Do bring along anyone you like.'

The ambassador couldn't wait to hear the princess's reply.

'What an interesting idea,' she managed, before rapidly moving on.

Martinez bowed low once again. The ambassador hurried after his royal guest. He was relieved when she stopped to chat to his wife, but the only sentence he caught was, 'What a frightful little man, how did he ever get invited?'

Once again, the ambassador glanced towards his study, and breathed a sigh of relief when he saw Becky walk out on to the terrace and give him a firm nod. He tried to concentrate on what the princess was saying to his wife.

'Marjorie, I'm desperate for a cigarette. Do you think I could escape for a few minutes?'

'Yes, of course, ma'am. Shall we go back into the embassy?'

As they walked away, the ambassador turned to check on Martinez. The besotted man hadn't moved an inch. His eyes were still firmly fixed on the princess, and he didn't seem to notice Sebastian quietly returning to his place just a few feet behind him.

Once the princess had disappeared out of sight, Martinez turned and beckoned Sebastian to join him.

'I was the fourth person to meet the princess,' were his opening words. 'Only the president, the prime minister and the mayor were presented before me.'

'What a great honour, sir,' said Sebastian, as if he'd witnessed the whole encounter. 'You must be very proud.'

'Humbled,' said Martinez. 'This has been one of the great days of my life. Do you know,' he added, 'I think Her Majesty agreed to have dinner with me when I'm next in London.'

'I feel guilty,' said Sebastian.

'Guilty?'

'Yes, sir. It should be Bruno who's standing here to share in your triumph, not me.'

'You can tell Bruno all about it once you're back in London.'

Sebastian watched the ambassador and his secretary walk back into the embassy, and wondered if his father was still there.

'I've only got as long as it takes the princess to smoke a cigarette,' said the ambassador as he burst into his study, 'but I couldn't wait to find out how the meeting with your son went.'

'He was shocked to begin with, of course,' said Harry as he slipped his BOAC jacket back on. 'But when I told him he hadn't been expelled, and they were still expecting him at Cambridge in September, he relaxed a little. I suggested that he fly back to England with me, but he said he'd promised to take a package to Southampton on the Queen Mary, and that as Martinez had been so kind to him, it was the least he could do.'

'Southampton,' repeated the ambassador. 'Did he tell you what was in the package?'

'No, and I didn't press him, in case he stumbled on the real reason I'd travelled all this way.'

'Wise decision.'

'I also thought about going back on the Queen Mary with him, but I realized that if I did Martinez would soon work out why I was here.'

'I agree,' said the ambassador. 'So how did you leave it?'

'I promised I'd be there to meet him when the Queen Mary docks at Southampton.'

'How do you think Martinez will react if Sebastian tells him you're in Buenos Aires?'

'I suggested it might be wise not to mention it, as he'd be certain to want Seb to fly back to London with me, so he agreed to say nothing.'

'So now all I've got to do is find out what's in that package, while you get back to London before someone recognizes you.'

'I can't begin to thank you for all you've done, sir,' said Harry. 'I'm painfully aware that I'm a distraction you could have done without at the moment.'

'Don't give it a second thought, Harry. I haven't enjoyed myself so much in years. However, it might be wise for you to slip away before - '

The door opened, and the princess walked in. The ambassador bowed, as Her Royal Highness stared at the man dressed in a BOAC captain's uniform.

'May I present Captain Peter May, ma'am,' said the ambassador, not missing a beat.

Harry bowed.

The princess took the cigarette holder out of her mouth. 'Captain May, how nice to meet you.' Giving Harry a closer look, she added, 'Have we met before?'

'No, ma'am,' Harry replied. 'I have a feeling I would remember it if we had.'

'Very droll, Captain May.' She gave him a warm smile before stubbing out her cigarette. 'Well, ambassador, ring the bell. I have a feeling it's time for the second round.'