We're standing on the Isabel II Bridge in Seville, a city renowned for its passion, yet one where the authorities seem to have lost their softer side. Uneven rows of padlocks glint beneath the sun, representing the lovers who signed them before flinging their keys into the river.

I thought I'd found a local tradition but then I stumbled across padlocks on the Pont des Arts in Paris, rusty padlocks in Spain's windswept Cabo de Gata Natural Park, and even sequined padlocks and handcuffs in the party city of Cologne.

The origin of the practice is unclear - padlocks have appeared in China for years at sacred sites, and there was a flurry of padlocking in the Hungarian town of Pecs in the 1980s, when university students locked them on a bridge next to the university either as a symbol of undying love or their determination to finish their courses. In 2007, the appearance of padlocks in the Italian film Ho Voglia di Te gave the tradition a boost, with reports of lovers' padlocks in Latvia, Russia, Korea, Italy and, some might say a little less glamorously, Southport.

So why do the authorities hate them so much? It all comes down to weight. Some structures simply can't support the bulk of 1,000 lovers' dreams, so every now and then sparks fly in Seville as angle grinders sweep the bridge clean.

This doesn't bother Pedro, though, as he adds another tiny padlock to one already there. He smiles at me. "For our son."

Abigail King is a blogger at lonelyplanet.com, and runs Inside The Travel Lab.

In Romance
07 June 2011 / www.bbc.com / By Abigail Kin