SARAH KERR has a confession to make ... she’s a pharologist and proud of it.

The 36-year-old is obsessed by lighthouses, and over the past seven years she has visited and catalogued hundreds of these beautiful, remote buildings around the UK.

During that time she met her husband-to-be at remote Cape Wrath Lighthouse in Sutherland – even their honeymoon was a light-bagging trip, and she has found time to have had two children.

Her obsession is such that Kerr, who lives at Portskerra at Melvich in Sutherland, has now produced the first authoritative trail guide to British lighthouses.

Husband Bob, 41, accompanies her on most of the trips – which have sometimes involved chartering boats and even a helicopter.

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But he is no stranger to adventure having attempted to conquer Everest six years ago.

He abandoned his bid as he closed in on the summit after losing vision in one eye with high altitude retinopathy – common among mountaineers who venture above 25,000ft.

The radiological protection officer is to make another attempt at conquering the world’s highest mountain so he can join an elite group of climbers to have conquered the highest summits on each continent.

He was also the first Briton to have climbed the highest peaks in the Arctic and Antarctic and completed all of Scotland’s Munros – peaks over 3,000ft – in December 2004.

But within a few months of his Everest climb he was marrying his lighthouse-bagging wife and on honeymoon in Northern Ireland ticking off more beacons.

The most famous pharologist is the Princess Royal who, as patron of the Northern Lighthouse Board, is on a quest to visit as many of Scotland’s 206 major navigational lights as possible.

But Kerr could certainly hold a light to her. She has ticked off most of the 294 in Scotland listed in her book – but the total also includes major harbour lights.

Her book details 612 throughout the UK, and Kerr has personally visited 503, so far.

All of the UK lighthouses owned by Trinity House in England and Wales and the Northern Lighthouse Board in Scotland and the Isle of Man have been automated since 1998.

Eddystone and Bishop Rock are the tallest lighthouses in the UK at 49 metres (160.7ft).

Berry Head lighthouse in Devon is believed to be the shortest major lighthouse in the UK at just five metres (16.4ft) tall.

The oldest lighthouse in the UK is still visible in the grounds of Dover Castle and is believed to have been built by the Romans around 183AD.

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The author Robert Louis Stevenson was a grandson of Robert Stevenson, who constructed 15 Scottish lighthouses – but Kerr says her favourite engineer of the famous family is Alan Stevenson, Robert Louis’s uncle.

Among his notable works is the Skerryvore Lighthouse, 12 miles southwest of Tiree.

The most isolated, formerly manned, lighthouse in the British Isles is Sule Skerry, built in 1895 and situated 37 miles from the coast of Orkney. It is also Kerr’s favourite.

Kinnaird Head was the first Northern Lighthouse Board light to be built on mainland Scotland in 1787.

Unlike many other rock lights that were built before it, Bell Rock lighthouse, located 11 miles off the east coast of Scotland, was built on a rock that was submerged under 16ft of water twice a day.

Isle of Wight-born Kerr’s obsession began after she took a month off from her communications job in London to visit lighthouses “because I love them”.

“I’m not sure how it all started, but I took the holiday and I haven’t stopped since,” said Kerr, now communications manager for Dementia Friendly Communities, a charity based in east Sutherland.

“I moved from London a year after I met Bob on my 2012 lighthouse tour. He was hillwalking at Cape Wrath and we talked for about 10 minutes on the little ferry back across the Kyle.

“I later found his email address from an article about him – and the rest is history.

“On that first trip – after months of planning – I set off with what I thought was a comprehensive list of lighthouses, but I found a number of others on my journey, particularly in Scotland.

“After my tour, I discovered even more I had missed which encouraged me to continue researching. This research expanded to incorporate island lighthouses as well as those in Northern Ireland, the Isle of Man and the Channel Islands.

“I have done the hardest ones and the book covers 82% of the main lights in the UK.

“It also includes those the Northern Lighthouse Board no longer own.

“While there are some printed publications and online lists available, most are either fairly geographically selective, include only the larger structures, or feature almost every lit aid to navigation.

“I felt those wanting, as I did, to visit all of the British lighthouses, or those interested in a specific area, really needed a handy resource to help plan, and take with them, on their adventures.”

During her years of lighthouse bagging, Kerr has had Seumas, five, and Caoimhe, two.

She says Shetland’s Muckle Flugga, North Rona and Sula Sgeir – where hunters from Ness on the Isle of Lewis each year kill 2,000 baby gannets for food – have been among the hardest to reach.

The Flannan Isles off Lewis – best known for the mysterious disappearance of its three keepers in 1900 – was also a difficult trip.

“I have hired boats – usually with island-baggers – and even a helicopter to fly over Mew Island off Northern Ireland,” said Kerr.

“Dubh Artach, northwest of Colonsay, was the scariest to reach – it is notoriously hard to land on and I thought we might fall out of the boat. We didn’t land.

“It has cost me thousands over the years. I daren’t count up. I have traipsed over hundreds of miles. I guess I just love a list and to tick things off.

“I have never seen a lighthouse keeper because the lights are all now automated, but I have met retired keepers,” said Kerr.

“I just love seeing the towers, and you go to some amazing places. It is incredible how these buildings were built in the first place.”

She added: “I just marvel at their construction and the people who built them – as well as the keepers who lived in them.”

The British Lighthouse Trail is the only book of its kind to provide a comprehensive listing of all lighthouses in Scotland, England, Wales, Northern Ireland, the Isle of Man and Channel Islands accompanied by practical advice on how to reach them. It is published by Whittles of Caithness at £18.99. www.whittlespublishing.com