Note: I don't know London very well so apologies if anything is wrong with my geography.

This story came about during a game of what I call "Situations" with andbreathe - one of those ones where you give characters numbers and then the other person reads out situations involving combinations of numbers. So andbreathe asked "Would 7 and 15 make a good couple?" and I looked down and said "Yes... YES!" They were Gaius and Mrs Hudson. A match made in heaven?

Merlin and Gaius had never been across to London before. It did occur to them that this was quite bizarre – having been around for about 1,500 years and never once left Somerset. So one sunny weekend they decided to pool together what little money they had accumulated since the Dark Ages (which actually added up to about twenty thousand pounds, seventy guineas and a heap of shillings) and take a train journey to the city about which they had heard many things, both good and bad. At any rate, it would be a good few days spent sightseeing. There was little else to do whilst waiting for the Once and Future King to rise again.

When they stepped off the train at Paddington Station they were quite surprised to see so many people. There weren't many people in Somerset, and it was nice to see more people than sheep. They went along with the bustling crowd until they realised that they didn't really have any idea as to where they might be going. Gaius had apparently booked himself into a small guesthouse on Baker Street, wherever that was: he had neglected to bring a map.

Therefore he went up to the first person he saw who didn't seem to be in a hurry, who turned out to be a small-ish, old-ish woman browsing the magazines in WH Smith's.

'Excuse me,' said Gaius, 'but could you tell me how I might get to Baker Street?'

'But of course! You take the –' The woman turned to them, and seemed to become momentarily speechless. 'You just take the Bakerloo line,' she said, a little more quietly than before.

'And where might I find that?' asked Gaius.

'The Underground, of course. Oh – have you never been to London before?'

Merlin and Gaius both shook their heads very definitely.

'Easy to get lost in London,' the woman said sympathetically. 'Tell you what – I'll just buy this magazine and then I'll show you the way, if you like.'

She picked up a magazine about housekeeping from the shelf, mumbling something like I'm not their housekeeper to herself, and Gaius and Merlin thanked her and said they would be very grateful but she didn't have to.

'Oh, no, it's fine, dears,' she said. 'I'm going that way myself.'

She went to the till to pay for her magazine and the romance novel she was clutching in the other hand. Whilst they were waiting for her, Gaius threw Merlin a relieved glance, but Merlin wasn't concentrating. He had been half-interested, half-worried whilst watching this whole exchange.

The looks Gaius and the woman had been giving each other had been especially worrying. The woman had been looking at Gaius slightly strangely, which could probably be explained by Gaius's robes, which he still insisted on wearing despite them having gone out of fashion in the twelfth century. But the look Gaius was giving the woman...

Oh God, thought Merlin. Gaius has fallen in love.

'Martha Hudson,' said the woman as they were leaving the shop.

Gaius and Merlin both started. 'Hmm?'

'That's my name. Martha Hudson. But you can call me Mrs Hudson. Everyone does.' She offered an awkward handshake from below her handbag firstly to Gaius, then to Merlin.

'I'm Merlin and this is Gaius,' Merlin said, as Gaius seemed to have lost his tongue.

'Are you on holiday in London?' she continued cheerily.

'Yes – just for a few days,' Gaius said eventually.

'See the sights and things,' Merlin added, staring up above him as they exited the station. The city was buzzing with activity and the air was slightly heady with the air pollution that was unnoticed by Londoners, but distinct to two men who had spent 1,500 years in rural Somerset.

'You'll enjoy London, I know you will.' Mrs Hudson smiled. Then, just as they crossed the road, she said, 'Ah, here we are. I'll let you get your tickets.'

'Thank you very much,' said Merlin, flashing her one of his best smiles and shaking her hand.

'Ooh, he's a proper gentleman, your grandson,' Mrs Hudson said to Gaius, beaming. 'I hope you enjoy London. Goodbye then!' And with a cheery wave she disappeared into the depths of the underground station.

They did not comment on her first comment as they had many times been mistaken for grandfather and grandson, and had decided that it was much easier to pretend that that was the case.

Merlin bought the tickets, for he had adapted to modern life, and indeed every passing century, far better than Gaius had, and they went down to catch the train to Baker Street.

'Friendly, aren't they, these Londoners?' Gaius commented as they walked onto the platform.

'Well, that one was.' Merlin shot a sideways glance at Gaius, who was looking rather happy.

'Yes...' Gaius drifted off into some kind of absorbing daydream and Merlin had to pull him onto the train when it arrived. Their conversation dried up until they had reached the Baker Street stop, as nobody else in the carriage was speaking and it didn't feel right, but even when they had emerged into the daylight Merlin found that Gaius was being worryingly silent.

'What?' he asked.

Gaius jumped. 'Oh, nothing. I was just wondering... Which is our inn, Merlin?' he asked, changing the subject.

'Guesthouse,' Merlin corrected him. 'Nobody calls them inns any more... It's this one.' He led Gaius towards a townhouse whose window was advertising vacancies and bed and breakfast.

Just then Gaius, about to step off the kerb, halted and looked to his left. Merlin followed his gaze and groaned as he saw that Mrs Hudson was crossing the road further up. For a split second Gaius looked as if he had been frozen; then he blinked and continued after Merlin.

'I wouldn't keep stopping when you're crossing roads,' Merlin warned him. 'Cars are faster than horses, remember?'

Gaius still hadn't got used to cars, despite them having been around for more than a century.

'Mm,' he said vaguely. It was only when they had reached the door of the guesthouse that his eyes left a point somewhere down the street.