I don't remember when I first had the crazy idea of walking a hundred miles around London in a single week in the company of Mitzpah my dog. On one level it seemed like a good way to raise sponsorship towards the cost of building my congregation's new synagogue and community centre. I wanted to do something which showed physical effort and personal commitment.

But that alone didn't seem like a good enough reason. A building for religious purposes required something more. I deeply believe that ends are always a reflection of the means. Therefore, just as our building had to aspire to represent certain values, - community, public service, social and environmental justice, a bridge between people of different faiths, as well, of course, as Jewish ethics, spirituality and learning, so my walk had to encapsulate those same values. I knew then what it was which had to define my route.

I spent six months in preparation, speaking to organisations as diverse as the The Woodland Trust, The Royal Free Hospital, The Hindu Temple in Neasden, World Jewish Relief, The Three Faiths Forum, and organisations which promote understanding between Israelis and Palestinians, and ask if a wandering rabbi with a dog in tow could make a muddy visit.

I decided to take the dog because the notion of walking for a hundred miles without him seemed absurd. Besides, he was definitely part of the appeal; a young and eager border collie, he was the photogenic side of the partnership. But his presence did raise certain logistical problems. Parliament, where I was to meet my MP, Dr Rudi Vis, then speak to the all party committee on inter-faith relations at the House of Lords, doesn't admit non-working dogs. But alternative arrangements were soon made. In the event, a congregant kindly took him down to the Underground for shelter from the driving rain, where he befriended a busker with a violin, I hope increasing his takings.

That's how I came to be at The Royal Free Hospital last Saturday night, where Professor Owen Epstein showed me the latest instruments for training doctors in the highly skilled examination of the intestines and colon, while I, squeamish at the best of times, stood close to tears watching the pictures on the simulator screen.

The next day my daughter walked with me to the mosque where I met two prominent Imams from the Middle East. 'It's so good that your child is with you', they said, 'We want members of the younger generation to get to understand each other better'. Again and again on my walk the theme of inter-faith relations came to the fore. 'How can we make our work even more effective?' I was asked at The Council For Christians And Jews. I raised the issue at the committee meeting in The House Of Lords: 'How, in the very moment when societies may be pulled apart by visceral religious and racial loyalties, do we create bonds of shared values and ties of common citizenship which hold us together as one family, one humanity, in spite of everything?'

The weather was less than wonderful. At least I couldn't complain that it was too hot to walk in comfort. The wind made the Thames like a sea as I followed the tow path into central London from Kew, where I was shown the remarkable work of the gardens in recording and preserving rare plant species. I was worried for the dog as the rain pelted down, but he made nothing of it, racing through the brush with delight. Despite the cold, the signs of spring were everywhere, alder catkins, glades of daffodils, violets in the meadow grass in Hertfordshire.

On Monday night I met leaders of World Jewish Relief at Liverpool Street Station. A statue commemorates the place where, almost seventy years ago, just under ten thousand children, mostly Jewish, were received into this country from Berlin and Frankfurt, Vienna and Prague, to face a future alone and far from their families. 'It wasn't until I myself became a parent', one lady who came with the Kindertransport told us, 'that I realised how hard it must have been for my father and mother to know that they were parting from us forever'. Earlier that day I'd petitioned my MP for more humane treatment for asylum seekers now.

On Tuesday I went to Great Ormond Street Hospital, where the Senior Chaplain Reverend Jim Linthicum and I prayed together for the wellbeing of all the children in the hospital's care and for God's guidance for all who bring healing. I was determined to visit hospitals and hospices because, for all the faults of our health care system, too many of us take it for granted too often and so add to the burdens of over-stressed staff by failing to express gratitude.

That day was my longest walk, about twenty five miles north east, past the Arsenal stadium, out along the Lee Valley canal and across Epping Forest to Theydon Bois. But I was bent on reaching the site where our community had recently planted 500 trees. A thin moon shone in the black sky when I finally arrived there, but John Brown of the Woodland Trust was waiting to offer a warm welcome. In ten years time, he explained, the roar of the M11 wouldn't be heard from here, only the singing of birds.

With all the walking I'd been concerned about the dog's paws. In the event, his pads fared better than my feet. My blisters are now healed and I'd set off again tomorrow if I could. My pilgrimage passed all too quickly and a week encountering so many people so passionate about their values has left me light-footed and inspired.

Jonathan Wittenberg is Rabbi at the New North London Masorti Synagogue