Daniel Radcliffe makes a smooth transition to a romantic leading man in this touching rom-com that should warm the cockles of even the most cynical of hearts.

The former Harry Potter star demonstrates a deft hand for comedic timing in What If, which manages to combine quick-fire, snappy dialogue with realistic characters that don't feel like cookie-cut out movie roles.

Radcliffe plays Wallace, a medical-school drop out who has had his heart broken and is taking a time-out from the world of dating. That is until he meets his perfect match at a party - the equally witty Chantry (Zoe Kazan). There's just one catch - Chantry is already in a serious relationship with Ben (Rafe Spall). However, there's no denying the spark between Wallace and Chantry and they embark on a platonic relationship that's anything but.

Wallace's best friend Allan, played by the always-excellent Adam Driver, meets his soul mate Nicole (Mackenzie Davis) at the same party, and their feverish coupling only serve as a stark contrast to his and Chantry's chaste companionship.

Wallace and Chantry try to negotiate the murky waters of friendship while ignoring their physical chemistry, leading to various ups and downs involving bust-ups with Chantry's beau, moonlight skinny dipping, a disastrous crossed-wires trip to Dublin and a pivotal greasy snack favoured by Elvis Presley.

Yes it all sounds overly kooky, but What If's charm lies in its spot-on casting of Radcliffe and Kazan, who will have you rooting for them from the word go.

Sarah McIntyre