Packing France and Guernsey into a weekend visit may sound ambitious, but on a mini cruise it's a breeze.

The wide blue bay is a vision of paradise in the early morning sun: Golden sand, a gentle breeze and the curving beach almost to myself.

Then I look in the other direction along the shore to see the face of conflict: A massive concrete bunker, presenting a narrow slit towards the waves and built to resist bombardment from ships.

Now I understand why our Fred Olsen cruise liner Balmoral stirred so much interest with an onshore expedition on the Channel Island of Guernsey entitled “The German Occupation – with the chance to explore and photograph a German gun emplacement”.

Guernsey’s collection of gun emplacements is among the world’s finest, and Castle Cornet, bastion of the English Crown for 800 years, fires an 18th century cannon each day.

A gentler outing on offer is a cycle tour of the island, taking in some of its 27 (mostly sandy) beaches and bays. With a speed limit of 35mph, Guernsey has drivers so careful that even amateur cyclists can amble along with confidence.

Cruise ships make about 120 visits a year to Guernsey. It’s a grand sight to pull back cabin curtains to see the capital, St Peter Port, basking in the sun.

There’s plenty to see in a few hours onshore: Beaches and bays, the house where the French novelist Victor Hugo polished the final version of Les Miserables between visits from his mistress, fine seafood, and so many bits, bobs and bunkers left behind by the Germans.

While Fred Olsen cruises have a reputation of caring for the over-60s, it’s clear to see the weekend voyages attract a wider market: Family reunions linking the generations, hen parties/girlie weekends, and even a male voice choir were all on board.

Departing Southampton on Friday afternoon we took in Honfleur in Normandy before arriving in Guernsey on Sunday morning – and returning to England on the Monday.

If the weather is good, these destinations make a fascinating double act.