The 84-year-old great-grandfather, who now lives in Victoria, Canada, was one of 600 Allied soldiers and civilians-turned-army volunteers who fought in the pre-dawn hours of December 19, 1941, in a deafening cacophony of gunfire and exploding grenades as the Japanese army took Hong Kong Island.

To commemorate their bravery that day, the Tourism Commission and the Agriculture, Fisheries and Conservation Department have set up a 4km heritage trail that traces the battle for Wong Nai Chung Gap, one of the bloodiest in the defence of Hong Kong. The trail encompasses the water-catchment area, starting off at Tai Tam Reservoir Road, across Sir Cecil's Ride and ends at the West Brigade Headquarters on Wong Nai Chung Gap Road. Along the way, signboards have been placed at strategic points to tell the story of the battle, and some of the Allies' armaments and defences are still visible.

The trail was the brainchild of local war historian Tony Banham, author of Not the Slightest Chance, The Defence of Hong Kong, 1941, and Bill Greaves, senior project adviser with the Antiquities and Monuments Office, who separately approached the Tourism Commission with their ideas three years ago.

Wong Nai Chung Gap lent itself to this project as there were two established trails there already, with plenty of examples of war heritage, such as gun emplacements and pillboxes.

Both men have voluntarily contributed their historical expertise to the project and Greaves hopes that this trail can eventually be extended to link to other areas of historical importance.

'It's a jolly good start that they've made,' says Greaves. 'But I'd like to see it go all the way to Lei Yue Mun [another battle site] to make it into more of a package. There's a lot of natural history on the trail as well, a lot of dragonflies, so it is not just about military history.'

Many of the photographs on the signboards, including some taken by Japanese war photographers, have been provided by historian Ko Tim-keung, co-author of Battlefields of Hong Kong. 'The photos were from various sources,' says Ko. 'But the majority came from the Mainichi newspaper and were used for propaganda purposes, of course.'

The Battle of Hong Kong began on December 8, 1941, when the Japanese army invaded the New Territories and ended on 'Black Christmas', when Hong Kong governor Sir Mark Young personally surrendered to the Imperial Japanese Forces.

December 19 was the day after the Japanese invaded Hong Kong Island, killing about 450 Allied soldiers and taking 250 prisoners. It was also the day that the only Victoria Cross of the campaign was earned, posthumously, by Warrant Officer John Osborn of the Winnipeg Grenadiers, who was killed when he threw himself on a grenade to save his comrades.

Following the battle for Wong Nai Chung Gap, the defence of Hong Kong Island was effectively split in two. Allied water supplies ran out when the Japanese captured the reservoirs and there was a growing realisation among the defenders that resistance to the overwhelming Imperial forces was futile.

'It was obviously impossible to defend Hong Kong,' says Banham. 'All you could do was slow [the Japanese] up.'

For Gerrard, that meant following orders from the various fighting units as well as he could in the mayhem. 'We were based with the headquarters of each of the fighting units,' he says. 'We were overrun two times. We didn't know what was going on. I was on wireless sets, where everything came through in code. We had telephone sets in the bunkers, but they weren't much use to us as I'm sure the enemy could tap them. Signals were responsible for maintaining lines.'

Critical to the Allied effort on December 19, 1941, were the actions of the Hong Kong Volunteer Defence Corps. 'One of the defensive positions along the trail was held by a platoon of No3 Company of the volunteers, and they held up the Japanese for 11 hours,' says local history enthusiast Martin Heyes, who gives tours of Hong Kong's war heritage sites. 'The position they were holding had been identified as a critical part of the line of advance that the Japanese were likely to take. The volunteers were manning two pillboxes which were able to look down on Sir Cecil's Ride, along which the Japanese came.'

That strategic viewpoint enabled the Allied forces to inflict a large number of casualties on the Japanese.

'Figures vary between 600 to 800 Japanese killed on that day,' says Heyes, standing next to one of the pillboxes on the trail. 'You can get some idea when you stand here just how horrendous it must have been.'

Briton Dennis Morley was a bandsman in the Royal Scots, when the Japanese invaded. He was involved in the counter-attack on Wong Nai Chung Gap later that day. 'It was dark as we made a counter-attack under Captain [Douglas] Ford, but we just couldn't do anything. They threw everything they had at us - grenades, sniper bullets,' recalls the 86-year old. 'We had to retire.'

His group held their positions for the next two days. 'We'd been going since December 8. We were tired, hungry, feeling awful. I can't remember whether we slept or not, I think we just got five minutes of shut-eye where we could,' says Morley. 'We were being sniped and everything. There was a Japanese spotter plane overhead letting them know where we were.'

Ko says the trail has been a long time coming. 'It's nice that eventually someone is looking into these wartime sites,' he says. 'But I don't understand why it has taken so long.' None of the second world war sites has gained legal protection, he says. Ko is curious to know why none of the pillboxes and other relics have been graded, and hopes that the opening of this trail could pave the way for more such projects.

'It's good that the Tourism Commission has finally done this, and I hope more sites will follow,' he says.

Banham says the trail will interest a variety of visitors. 'Obviously, there's an appeal to foreign visitors, especially from Canada and the UK,' he says.

'But, more significantly, it will be of interest to local people and to [visitors] from the mainland, who may know nothing about this piece of history, and yet because it's all part of the Sino-Japanese war, may find it fascinating.'

Morley and Gerrard were later shipped to Japan as prisoners of war.

'You spent a lot of time forgetting it,' says Gerrard of his war experiences. 'Now we're trying to put it into the history books. You see, when we got back, we were pretty well ignored, people had had enough of war. And ours was a losing one too.'

Morley still mourns his fallen comrades. 'I'm very emotional, I'll be honest. I cry,' he says. 'Hong Kong couldn't be defended under any circumstances. We were hostages to fortune. You think of all those that you knew. They were only kids.'