If you drive to your walking start point then you can take as much stuff as you can fit in your car then choose which items to leave and which ones to lug round at your convenience, you can even have a spare set of clothes, and footwear, waiting on your return. Else, careful planning is necessary as space is a premium, unless planning to haul round a 80L rucksack all day.
Some top forty climbers & items that have fallen by the wayside...
Mobile Phone - never had to use one in an emergency, and you may find getting a signal tricky if you have to. Always handy if only to inform your nearest and dearest if missed train or transport and will arrive home later than planned. Usually remains turned off in rucksack - to save batteries but mostly to reinforce sence of solitude. Light weight, quick drying trousers with zip off leggings - Once your've warmed up, give your legs some air - will have to remove boots first though. Surprisingly, leggings zipper has never malfunctioned. Heavy Duty Rubble Sacks - my big plan to combat impassable mini floods (nothing worse than wet socks right at start of walk) put over each boot then hold on tight to tops, lasted a couple of walks then were abandoned in very heavy mud somewhere. Medical Equipment - Variety of plasters (including Blister ones), micropore tape, Sudocream, Bite & Sting cream and Insect Repellent Spray (for when walking next to sewage plants). Gloves - Haven't yet settled on a favourite pair, woollen are warmer but get wet easily - leather and synthetic feel a bit overkill. Gaiters - Every walker goes through a phase of wearing gaiters, its a rights of passage, its a piece of equipment designed especially for us. In the end we all end up just tucking trousers in our socks. Ear Muffs - useful when suffering from earache. Map PVC Case - see Gaiters.
Now for the top ten countdown, pop pickers!
10: Hat, wooly or brimmed
Wooly hat in winter to help keep ears warm and to protect them from constant wind noise. Brimmed in summer for portable shade, also protects back of neck from sunburn (some chance).
Full of hope at the start of a bright and clear day? This is England - its gonna rain. Your choice is a small foldaway - easy to carry in rucksack side pockets (see below) but has inherent design faults so will probably miss-function when you need it the most - like collapsing in driving rain on the South Downs. Or you could get a proper high price umbrella which will keep the rain off and stand up to high winds (although beware wind changing direction) but in close woods will just be a hindrance - also, it hurts a bit when you leave them behind on the bus or train. At the moment I'm in between worlds, using a brolly from M&S which is a cross between the two but just about fits in my rucksacks side pocket (although I feel like Boba Fett with it sticking above my head).
8: Boot cleaner & anti-bacteria hand wash gel (chart entry)
Cleanish boots are essential if want to re-enter polite society whether its on public transport or getting in bits for your tea at your local supermarket. I've recently started buying Punch Shoe & Boot Wipes but used to carry a mud sweeper boot cleaner ball but then reverted back to ancient stick technology for a good 5 years. Alternatively could pack some light weight flip flops for the journey home and bag up your dirty boots. Something you can't do with your hands, hence hand wash gel. Makes them smell nice if not entirely cleaning them.
7: Waterproof & windproof jacket
Will need two types - a light weight, light shower proof jacket for summer showers which you can stuff in rucksack and a more weightier one, which your'll wear all day in winter. I don't believe their rain proof claims after spending whole day in driving rain - putting faith in my first and only North Face jacket and ended up truly soaked to the bone. Luckly, I wasn't up Everest and was saved by hand dryer in toilets at Haslemere Railway Station. This is also why I carry an umbrella. My current winter jacket has a nice big chest pocket which fits a whole OS Explorer Map.
6: Rucksack & dry sack
Smaller the better. Maybe with some breathing space for your back. Need side pockets big enough to kit 750ml water bottle and for umbrella. This fits the bill. - black, obviously. For double protection from rain - or falling in river - can also double pack everything in a dry sack.
5: Nutrition & hydration
Never get that hungry on walks, using lunch to break up the walk and for a bit of sit down. Getting thirsty is another matter, a few summers ago whilst on a costal walk I ran out of water (due to miscalcutaing route distance and taking prolonged wrong turn) and with the heat and extra exertion got so thirsty was contemplating asking the next walker I saw for a sip, but never came across anyone and by the time I entered Hastings suburbs had resigned to waiting until finding open shop. I must say though, the anticipation of thirst quenching is up there with your first few Christmas (when your at an age when presents become expected) - but it did ruin walk.
4: Compass & Dedicated GPS device
For me, one of the most satisfiyng things about walking is the oppertunity to get lost (as long as my water bottle is full). Then to use a device which pre-dates Christ to guide you back to safety. No batteries, no menu systems, no IC chips. It's also fun to learn how to use it, I promise. However, when in an area with track overload and you have to pin-point your position on the map, reluctantly get out your military graded GPS device and dial up Navstar. This does force you to learn your National Grid
3: Ordnance Survey Explorer printed maps
Long live paper maps! For walking you really need the Explorer range from Ordnance Survey. These use a scale of 1:25 000 (21/2 inches to 1 mile). These maps will become your closest friend in the field and also keep you company late at night, as you graze lovingly upon their contours - planning routes and establishing new footpath connections. You buy them at most bookshops and WHSmiths. If visiting a place for one off walk can see if your local Library holds the map your after - although it would have properly been checked out the day before, and not all Libraries hold the entire range (but I think every Library will hold the map for the local area). After you have amassed multiple copies of the same map you can contemplate the unthinkable - cutting them up! This allows you to store smaller section of map in your trouser pocket, useful during summer hikes, but you have to stay within the area you cut out. I always keep a whole intact map for route planning, and to appease the map gods if they ever look unkindly on my defacement.
2: Walking boots & socks
O.K - these should really be at Number 1, but recently have had to re-evaluate my relationship with my feet and sitting down has become more important. Before this mind shift I was quite happy to squeeze my feet into a pair of these for days at an end. If you go for non-leather the waterproofing comes from the inner layer of boot. This is basically a sewn in sock which has very small holes which allow air to pass through but not water droplets. After walk make sure to clean out inside of boot as any small debris can tear this fabric, and so make waterproofing redundant. Recently I have been allowing my feet a bit of room with these (the extra wide size - in brown) which I got from this shop. For socks, I'm sold on the SmartWool brand. Although with the price you might want to learn darning skills, or relegate holey socks to lounge wear.
1: Foam seating matt
The original flat-pack furniture, making any flat spot a possible resting place. Even carry one in my work bag. Photo shows my delux walking version, thought I brought from Clas Olsen, but looking on website could only find my works one so will have to take care of deluxe version and make sure to pack it away after sit down and not leaving it there.