The scene in the Old Government House Hotel could not be further removed from the horrors of war. There is a soft swell of conversation as afternoon tea is served, a clink of cutlery on crockery, the discreet burble of tea being poured into china cups. Somewhere outside, the clouds part and light floods the lounge. I reach for another scone, ladle on a hearty dose of jam and cream, and marvel that, in this context, 70 years seems an eternity. Rewind those seven decades and Guernsey's only five-star hotel – pitched on the hillside above the harbour in the capital St Peter Port – would have been home to a decidedly less relaxed atmosphere. Seventy years on: St Peter Port in Guernsey is one of the key locations for the Heritage Festival . During the German occupation of the Channel Islands (30 June 1940 to 9 May 1945), this stately retreat was commandeered as the General Staff Headquarters. Invading officers would have stalked its corridors. By April 1945, they would have been wearing sour expressions as the tide of conflict turned back on Berlin, and the Channel Islands – bypassed by the D-Day fightback of ten months earlier - awaited their salvation. That eventual liberation is being celebrated again this month – and with gusto. The ongoing Channel Islands Heritage Festival (3 April–11 May) is a five-week hurrah of history, parades, concerts and food that will unite most of the archipelago – Guernsey, Alderney, Jersey, Herm and Sark. This is no small feat. Fiercely individual, the islands have never before combined to stage a big event. But here they have common cause. Liberation Day itself will turn St Peter Port and Jersey's capital St Helier into swirls of people and music. It is not difficult to find traces of Guernsey's harrowing half-decade. The occupation lingers in the old German fortifications that litter the coastline – the swarthy, sinister tower of Fort Saumarez which rears up on the west coast; the similarly menacing Fort Hommet in the north. Intrigued, I stroll into the stiff winds which burst up from the sea to walk around the hard muscle of Pleinmont Tower, on the south-west shore. It is an oddly unnerving experience, the pillar-box slots in the bastion's sides eyeing me quietly. When I face the water, I almost expect to feel the chill metal of a machine-gun barrel on my neck. Coastal curves: Guernsey's dramatic shoreline includes the wide expanse of Portelet Bay . You can go further into Guernsey's wartime heritage. What appears to be a car park behind La Colinette Hotel on the western outskirts of St Peter Port reveals itself as the hub of enemy communications in the Channel Islands. Hidden down a damp flight of stairs, the former German Naval Signals Headquarters is all but invisible unless you know it is there. This, of course, was the point. Its unremarkable door gives onto a vast underground space which once hummed with radio chatter, semaphore murmur and serious conversation. German signs and instructions are still daubed onto the walls. The bunker will be open to the public as part of the festival – its secrets brought into the light. The German Occupation Museum at Les Houards offers further perspective, flitting from frivolity to fear – on one hand the photo album of Freda Oliver, a local girl who dated (and married) a German officer; on the other, exhibits on the inevitable fate of the island's Jewish population, and copies of the Guernsey Evening Press turned to propaganda sheet. The darkness of life under Nazi rule is most obvious at the German Military Underground Hospital, at La Vassalerie. This enormous labyrinth was carved out by the slave-labour sweat of prisoners of war – plenty of whom died in the process. As did many of the injured German troops brought here from France after the D-Day landings. With its dank passages and horror-film ambience, the hospital is the definition of an unhappy building. An island guardian: Mont Orgueil Castle has protected the east coast of Jersey since the 13th century . The picture is replicated 27 miles to the south-east. Jersey is a short hop from Guernsey – around an hour by fast ferry, less by air. Here, the Jersey War Tunnels – another military-medical complex – have been restored into something less frightening, with museum displays and fascinating facts slotted into the long tunnels. The side-effects of occupation can be seen here – the breakdown of society apparent in transcripts of letters where neighbours informed on each other about hidden radios and petty jealousies. But so can the joy that liberation brought. Glorious video footage shows euphoria in St Helier as the news of German surrender broke; the Union Jack being hoisted at the Pomme D'Or Hotel. The hotel came to symbolise the Channel Islands' moment of deliverance. In a way, it still does, peering across what is now called Liberation Square, where a tall bronze sculpture captures seven people in the act of raising the flag – laughing, as if they are flying a kite. Other echoes resound across St Helier. The Jersey Museum and Art Gallery has a catalogue of copies of the Jersey Evening Post dating back 125 years, its photos recalling the war era in day-by-day detail (albeit through a fog of strict German control). The nearby Maritime Museum proffers the Occupation Tapestry Gallery – a montage of bright images, stitched by islanders for the 50th anniversary of liberation in 1995, which depict Jersey brought to heel – armed troops in the streets, the island hemmed in by a ragged circle of fire. And the Jersey Archive is host to a remarkable resource – over 30,000 of the Occupation Registration Cards which were forced on islanders by the Nazi authorities. There are no smiles here – just a series of furrowed brows and unhappy faces. Bright days ahead: A view of the pretty coastal enclave of Gorey from the ramparts of Mont Orgueil Castle . The heaviness of the German bootprint is perhaps summed up by Battery Lothringen – a concrete watchdog which looks like it might still bite. This colossal bunker – which will also be accessible during the festival – 'protected' St Helier from the far side of St Aubin's Bay. The stairs into its depths seem to go down forever, to gun posts, control rooms and sleeping quarters – the decades peeling away as I walk in the firm footsteps of the enemy. And yet, just seven miles north-west, it all feels like a bad dream. St Brelade's Bay Hotel gazes at the water in a rather more benign manner. In the summer of 1940, it was another German outpost, requisitioned as a hang-out by Luftwaffe pilots. It is not difficult to grasp why it was coveted. Over breakfast, I peer out of the wide restaurant windows – at waves rolling gently up to the beach, and at St Brelade's, a pretty block of an 11th century church whose graveyard hovers above the sand. There is no stomp of marching boots this morning – but for five weeks, the Channel Islands are remembering a time when there was. Aurigny (01481 822 886; www.aurigny.com) and Flybe (0371 700 2000; www.flybe.com) serve Guernsey from various UK airports. British Airways (0844 493 0758; www.ba.com) and easyJet (0843 104 5000; www.easyjet.com) fly to Jersey. Double rooms at The Old Government House Hotel (01481 724 921; www.theoghhotel.com) cost from £188, including breakfast. Doubles at St Brelade's Bay Hotel (01534 746 141; www.stbreladesbayhotel.com) start at £140, with breakfast. Channel Islands Heritage Festival: www.visitchannelislands.com/heritagefestival . Guernsey tourist information: www.visitguernsey.com . Jersey tourist information: www.jersey.com .
Channel Islands were the only parts of the British Isles occupied in the war . May 9 is the 70th anniversary of the islands' liberation from German rule . Guernsey, Jersey et al are marking the occasion with a five-week festival .