I have lots of good reasons.

• The weather in London sucks.

• We only have a few hours of daylight most of the year and the roads are crowded then.

• I walk a lot anyway. At least 30 minutes every day, often an hour or more.

• I'm convinced by something I read that physical exercise doesn't actually contribute to weight loss and may, by increasing appetite, actually promote weight gain.

• I have 200 things on my to-do list, so who has time for bike riding.

• My bike had been put (not by me) to the back of our dusty, damp shed. It was dirty and the tires were flat.

But today -- like yesterday -- is a stunningly beautiful London day.

And as I told friends yesterday, there's just no excuse on a day like today to not cycle.

On Friday, also a beautiful day, I purchased a mini bike pump and a reflective jacket for night riding. (Too bad I forgot to bring my London Cycling Campaign membership card; I'd have saved 10%.)

So after 18 months, I've finally added air to the tires (couldn't figure out how to do this, then went here), taken the bike out of the shed, dusted it off and gone for a spin.

Not much of spin -- not even a full mile, really. But just enough to get the feel of what it's like to be on a bike again.

I think I'll go out again now -- take my lock, my wallet, maybe actually go somewhere. More later.

UPDATE: Just did a two-mile spin nearly to East Finchley through some back roads, and back. Tired! But delighted that today equalled 1/10th of all the riding I've done so far on this bike.

Odometer at start: 32.8 miles
Odometer at end: 35.7
Ride: 2.9 miles (4.7 km)

Not much opportunity to ride a bike, except a stationary bike in the gym.

But I have just biked through a beautiful neighborhood in Queens, New York with one of my oldest friends, who took me on his favourite route -- including a vigorous spin through Forest Park (see photo to the left).

It was around 75 minutes of solid cycling, far more than I usually do at home. I thought holidays were supposed to be restful! Anyway, it means that I can eat donuts now without feeling guilt.

Or a lot of guilt.

The more I biked, the further back I pushed my target. First, it was to get to Muswell Hill and back. Then it was to get the odometer up to a nice round number (30 miles). Then, to have completed 6 miles today (that would have added 25% to the 24.71 miles I'd done in the last month) -- and finally, to complete 8 miles. Why 8 miles? So that I could say that I'd increased the total number of miles I've ridden by one-third -- from 24.71 up to over 32.71. Which I did.

From the numbers above, you can tell I'm not taking the bike out nearly as often as I should. But I have to say that today was more pleasant than usual and I'm more comfortable. I'm limited a bit by the fact that my neighborhood is on top of a hill, and I spent the last 3 miles or so spinning around side streets here. I'd actually prefer to be going from point A to point B, but point B is always at the bottom of some hill ...

Anyway, that was almost 55 minutes of riding, which according to my trusty Palm translates as 689 calories burned -- which is the equivalent of burning off nearly 100 g of weight, or eating one of these:

So I repeated my classic ride to Muswell Hill and back, a total of 5 miles in 30 minutes. According to my trusty odometer, until now I'd only biked 19.78 miles -- in other words, it seems as if I've spent more time writing this blog than actually riding the bike. (Not true, but it does look that way.) But now with cooler weather coming (British summers are not usually this bad) it will be more tempting to go out. Especially on a cool and pleasant Sunday morning, with no traffic on the road.

For a person of my weight, riding a bike between 12-13.9 miles per hour, I should burn off 755 calories. Pedalling faster, between 14 to 15.9 miles per hour, I would burn off 944 calories. Those are the numbers from my Palm-based Diet and Exercise Assistant software. They make for pleasant reading and really encourage me to get on my bike.

But these numbers vary wildly depending on the source. For example, according to the Nutristrategy site, biking 10 - 12 mph making a "light effort" would burn off only 531 calories an hour for a person of my weight.

Faqs.org tells me that a 190 lb person pedalling 12 mph will burn off even less -- 472 calories per hour.

And according to Diet and Fitness Resources, a UK site, biking at 5 mph (perhaps a more realistic pace) would burn off only 240 calories in a hour (they don't say for what weight). This sounds like even less than what one burns walking, which might be the case if you are only gently gliding around on a flat surface and hardly pedalling at all.

Obviously there are other factors -- such as the difficulty of the ride (riding uphill will burn off more calories), water loss (perspiring a lot will lead to temporary weigh loss), and one's own fitness level.

And there are countervailing forces at play as well -- the more and harder one bikes, the more muscle mass gets built up in one's body. For this reason, many top athletes (and I think all players in America's National Football League) are technically considered to be obese, as their muscle weight gives them a body mass index in excess of 30.

Back to normal, middle-aged, overweight blokes like myself. Let's say I want to lose 16.6 kilos (which is a great deal, I know). That would require me to burn off 116,200 calories above my normal calorie expenditure. Biking half an hour a day at a 5 mph clip would expend 120 calories, so it would take 968 days to reach my goal. Knock off a day a week for resting, and basically we're talking about three years. Yikes.

The key here is not so much the intensity of the effort (biking half an hour a day at a moderate clip will not kill anyone) but persistence.

Have a look:

Maybe. First reviews say it's not comfortable enough to ride for very long. But it does look cool.

I just got back from riding through East Finchley, Hampstead Garden Suburb and Big Wood, over to Temple Fortune to the Marks and Spencer supermarket, and back. The ride through Big Wood was less pleasant than I thought on account of the shoddy condition of the path -- a mountain bike would have been better for this. But the Wood was quite empty, the weather perfect -- I can't complain.

This was my first "shopping ride", and I didn't remember or realize how much harder it is to bike with a full backpack. But you get used to it.

I was a little scared of the ride back up the hill to East Finchley, having remembered that this nearly broke me 6 or 7 years ago when I last attempted it on a bike -- but it was less difficult than I remembered. Practice will make it a breeze. It was the first time I used the lowest gears on my bike -- and, of couse, I managed to get the chain to fall off in the process. A learning experience all around.

Thank goodness there was no audience ...

P.S. The whole ride, both ways, took 33 minutes, or as I like to think of it, 411 calories, which is the equivalent of one of these:

On Yer Bike in Finchley

Waitrose, North Finchley: Starting point for group rides

I've just come across this very new blog, written by someone in my neighborhood: On Yer Bike in Finchley. Until I saw it, while I realized that there were group rides organized by the London Cycling Campaign, I wasn't aware of spontaneous, self-organized community rides as well.

MoveThat.co.uk's London Cycling Forum

Many of those can be found on MoveThat's London cycling forum, a place alive with people asking others to ride together. This is where I first read about the group rides being offered on On Yer Bike in Finchley.

After I attempt my first group ride, I'll write something up here.

I am speaking, of course, of London at 5:30 A.M.

I took my bike out this morning for a 37 minute spin from my neighborhood (Finchley Church End) through East Finchley over to Muswell Hill and back for a total of 5.8 miles.

The streets were not entirely empty. I did pass one other cyclist, two pedestrians, a couple of Express Dairy eco-friendly vehicles delivering the morning milk, one early morning bus, and about three cars.

The sun rises at 4:51 on a summer morning like this one in London, meaning that cyclists can get a head start of an hour or two before drivers get out on the roads with their cars. On weekends, this should be even better. Sunday mornings in north London, the roads seem completely empty.

This will not be the case in winter. When the sun rises after 8:00 AM and sets before 4:00 PM, there will be nothing like this. So during the next few weeks, for cyclists who can awaken with the sun (or have no choice, like myself), the cycle-friendly city we dream of is there for the taking.

For me, the timing is perfect -- until now, almost all bike magazines seem to have been aimed at competitive racers or mountain bikers. But what about the vast majority of us who use our bikes for leisurely cycling?

It's a promising idea, but the magazine is disappointing.

(The website, by the way, is an empty page.)

There are a couple of first hand accounts, but to be honest, the London Cycling Campaign's magazine has a lot more of this. Mostly, this seems to consist of ads, and ads barely disguised as articles. For example, there's a long article reviewing a few bikes, all of them sold by Evans Cycles, reviewed by Evans Cycles, and the conclusion is -- they're all great, just come down to Evans Cycles and buy one. I think for the appearance of honesty, they might have given one of the bikes a lousy review, but they didn't.

You can, however, win a bike by sending an email to eye.comp@kelsey.co.uk with the word "Schwinn" in the subject line and in the text -- give the correct answer to their question, which is "2".

I love to walk, and walking has been my primary exercise for years now. Thanks to both walking an hour or so yesterday, and biking for more than 30 minutes, I burned off a considerable number of calories -- a total of about 725. That's 382 in 31 minutes of biking, and 343 in 55 minutes walking outdoors. (I don't count walking up and down stairs in the house.) If I could sustain that every day, I'd lose a kilo every 10 days, and 36.5 kg over the course of the year.

The route took me downhill almost all the way to a large open field next to a woodland -- a place I didn't realize even existed -- and the route back was, um, uphill most of the way. I was fine until the very last, sharp incline (again, over railway tracks) -- and felt some pain (not much) in my arms and legs. This pain went away very quickly after getting off the bike.

(Purchased at Action Bikes in Finchley.)

It's a Dawes, a hand-built British bike made by a Birmingham company.

It's the first bike I've purchased since 1999 -- and that bike was only ridden a few times before being abandoned, and later donated to charity.

Previously, I owned bikes continuously from childhood right up until 1998. My favorite -- and longest-lasting bike -- was an Italian-built Atala, a very light, white road bike that I purchased in Ithaca, New York in the summer of 1974. I rode that bike all over upstate New York, New York City and Long Island before taking it to Israel, where I continued riding it well into the 1980s and, I think, 1990s.

This new bike cost around £200, and I've added on a cheap bike computer to track distance mostly.