William IV, Kensal Green, London

When the William IV in Kensal Green reopened after a one-month refurb in March, the spruced-up interior wasn't the only new thing about the north-west London gastropub: a Spanish menu had been introduced.

Although the William IV was well regarded for its classic gastropub offering of steamed mussels, sirloin steak and seared salmon - it was shortlisted for the London Evening Standard's Pub of the Year award in 1999 - co-owner Patrick Morcas felt a change of culinary direction was needed.

"When I started seeing companies that already own 200 pubs opening up gastropubs, I thought it was time to do something different," he says.

With Thai the default food option for many pubs, Spanish might not seem like the most obvious cuisine, but for the past 16 years Morcas has co-owned El Parador in Camden Town, so he knows a thing or two about Spanish cooking. And tapas lends itself to the pub setting - one or two plates can be eaten as snacks with a cocktail or pint in the 60-seat bar, or a full meal can be ordered in the table-service dining room, which seats 40.

"It's opened up the drinking side of the operation to eating," says Morcas, "and our food turnover is up by 13%."

Lunchtime trade varies, but can be up to 60 diners - "a mix of local mums, small businesses and Portobello trendies", according to Morcas - with a three-for-the-price-of-two tapas offer enticing weekday customers. Evenings usually reach 100 covers. And, although the busiest shift is Sunday lunch, when a traditional English roast is still served and the whole pub is full (including the 60-seat garden in fine weather), the new Spanish menu has been well received.

"We've been pleasantly surprised," says Morcas. "There's been very positive feedback."

The menu - with 17 vegetarian, 11 meat and 11 fish tapas - changes on an ad hoc basis, with less popular dishes being removed as and when, and ingredients being used in season. Squash has recently been replaced by sweet potato, while Dorset crab and diver-caught scallops have been added.

The best sellers are, unsurprisingly, the more familiar dishes: chorizo pan-fried with red wine, baby onions and pancetta (£5), meatballs in tomato sauce (£5) and tarragon chicken goujons pan-fried with asparagus (£5.25), but the black pudding with fried egg (£5.50) is popular, too.

"It's not a greasy-spoon black pudding," explains head chef Marcos Georgiou. "We pan-fry it with smoked bacon, chickpeas, onion, tomato salsa and paprika, then deglaze the pan with sherry vinegar and serve a fried egg on top."

Georgiou is helped by only one sous chef, but says the kitchen is not understaffed. "It's the kind of menu that you don't need a big brigade for. The secret of good tapas is the mise en place. You have to be ready for evening service, but the hard work is already done."

The wine list, too, has become more Spanish, although, again, customers tend to stick with what they know: two Riojas (£15.75 or £19) or French Chardonnay (£15.50) rather than a Ribero del Duero (£28.50) or Txakolin de Guetaria (£19), a white that Morcas describes as "a lovely wine with a slight effervescence that's great with fish".

Morcas and his business partners Nick Daniel and Carlos Horrillo own another gastropub, the Mall Tavern in Notting Hill, but there are no plans to introduce a Spanish menu there. Instead, the trio hope to open a tapas bar in Chiswick or Ealing, although there's nothing definite as yet.

And, who knows, if Spanish takes off as the next big gastropub trend, they might need to find another new menu for the William IV.

What's on the menu

• Spinach, onion and mushroom tortilla with harissa, £5
• Red pepper and feta cheese croquettes, £5.50
• Whole globe artichoke with sauce gribiche, £5.65
• Confit belly of pork with caramalised onions, £5.25
• Chargrilled rosemary lamb cutlets with confit garlic, £7.25
• Pan-fried foie gras with chilli jam and smoked paprika, £7.50
• Chargrilled sardines with salsa verde, £4
• Rice with seared scallops, parsley, lemon and garlic, £6.50
• Whole boiled crab with mayonnaise and bread, £8
• Apple and mixed berry crumble with cream, £4.50
• Red-wine-poached pear with caramel sauce, £4.50
• Selection of Spanish cheeses, £6.50

William IV, 786 Harrow Road, London NW10 5JX. Tel: 020 8969 5944
www.william-iv.co.uk