The protesters, which VetSurgeon.org understands comprise six veterinary surgeons and 30-40 pet owners, started their march in Parliament Square and are now bearing down on the RCVS Headquarters in Horseferry Road.
The campaigners are, we are told, protesting against the RCVS position statement on complementary and homeopathic veterinary medicines.
No word yet on how the College proposes to defend itself from the hoard; certainly no sign of any cauldrons of boiling oil atop the battlements, nor any riot police yet in evidence.
More news as it happens. VetSurgeon.org has a photographer on the ground ...UPDATES
1:00pm: The protesters have arrived at Belgravia House. A couple of protesters are armed with umbrellas, presumably to guard against the ever-present risk of overdose. It's getting messy: we're hearing that they've blocked the pavement. Wait up. Someone has emerged from the College to speak with them. Well hello, Mr President.
1:01pm: We were hoping that some of the protesters might, I dunno, handcuff themselves to Belgravia House or something. But after a tense standoff lasting over 36 seconds, it looks like the protest is petering out already. Apparently they've started dispersing to the park opposite.
1:02pm: Yup, they've all gone off to the park now. This may go down as one of the shortest protests in history.
1:16pm: Word has it they've headed off to the White Horse and Bower.More photos of this momentous occasion to follow ...
1. The seasoned campaigner is always careful to choose any banner that appears over their head with great care.
2. It was a beautiful march. A big march. The bigliest. Haven't seen that many people on the street since Donald Trump's inauguration.
3. The RCVS headquarters under siege.
4. Millie the dog (perhaps better called 'Millie the anecdote') illustrates the flawed thinking behind homeopathy.
5. Nobody told this campaigner than homeopathy wasn't banned in the first place. You can get it from any tap.
6. RCVS President, Professor Stephen May, presumably wishing he'd taken the day off work.
7. It took some hours moments before the crowd dispersed fully and life in London was able to return to normal.
3.43pm: The Royal College of Veterinary Surgeons has issued a statement following the march, which says:
The Royal College of Veterinary Surgeons today met a delegation of around 40 animal owners and veterinary surgeons who wished to voice their concern about a recent position statement by RCVS Council on the use of complementary and alternative medicines, including homeopathy.
President Stephen May and CEO Lizzie Lockett received a copy of an online petition that was set up following the statement, which has since received around 15,000 signatures, including around 11,000 from supporters in the UK.
Stephen and Lizzie also took time to hear accounts and stories from the supporters, and to listen to the points they wished to raise.
In view of the cold, wet weather, the College had laid on some hot drinks for all the visitors, and invited the delegation inside, but these were declined.
Stephen said: "We were pleased to be able to meet our visitors today and to receive their petition, although it was a little tricky trying to answer questions on a busy London pavement!
"We continue to recognise that homeopathy and other complementary therapies are popular amongst some animal owners and certain members of the veterinary profession, as indicated by today’s delegation, but it is worth reiterating that the RCVS Council statement does not ban their use.
"What it does state, is that in order to protect animal welfare, we regard such treatments as being complementary, rather than alternative, to treatments for which there is a recognised evidence base or which are based on sound scientific principles.
"This is similar to the position that we have held on complementary therapies for many years, but we will always be happy to receive and consider scientific evidence that demonstrates their efficacy."
I wouldn't hold your breath.
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Six vets in the group .... but they make as much noise as six thousand!..
(It’s a standard anti-homeopathy joke)