Should have been to B+Q to buy a love lock and leave it behind us on a bridge in Venice. A lot of the bridges have clusters of locks attached. I remember this in Paris when we went there for our 20th wedding anniversary. This is the Accademia bridge which crosses the Grand Canal.
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Our son, ever practical, suggested that instead of throwing the keys into the canal to ensure everlasting love, the man should hold on to the key incase he ever got a divorce so he could come back for the lock!