Where in London? Wartime Wren dispatch riders

Royal Navy Wren dispatch riders somewhere in London, circa 1943.
But where?

I recently came across a photo emailed some time ago by a reader named Douglas in Dania Beach, Fla. It shows British Royal Navy Wrens serving as dispatch riders during World War II.

In the photo, the young women on motorcycles roar in formation under an archway in a posed publicity photo. (Note that none of the men in the photo is stealing a glance at the camera — obviously warned, to make it look realistic.)

Where is that archway?

The truck at left bears the initials "R.N." For Royal Navy, I presume; and the van facing us behind the riders has, again, "RN" at the bottom of its windshield.

Other photos of Wrens on motorcycles (probably these same women) were clearly taken in London. Where else in London would all these Wrens and Royal Navy vehicles be, I guessed, except at the Admiralty building?

Admiralty Arch, London today. Note side street to right with small archway.

The location is a side street called Spring Gardens that runs around the massive Admiralty Arch at the end of The Mall in London. The little archway is insignificant compared to the enormous Admiralty Arch, and so is apparently ignored and rarely photographed.

Admiralty Arch, finished in 1912, adjoins the old Admiralty building (thus the name). The Wrens' little archway links the offices inside the Admiralty Arch to the old Admiralty building.

Composite photo with color arch and background from Google Earth.
The setting has changed little since World War II.

Spring Gardens is a lovely name, but the gardens are gone. The street was named after the gardens previously on the site, which featured a trick fountain. The gardens had been named after Sir William Spring, 2nd Baronet, according to Wikipedia.

This group of Wrens and motorcycles served as photographer's models.
Only Triumph PMP 195, shown in other photos, is missing from this group.

The riders are probably the same women seen in other photos and a film clip from the era. This group of Wrens seems to have spent a day buzzing around the Victoria Memorial in front of Buckingham Palace and elsewhere in London for photos.

I found these photos on the blogs Riding Vintage and Vintage Everyday.

Rider of SHX 123 opens her pouch. Buckingham Palace in background.

SHX 123 is in naval paint with RN 6908 stenciled on the tank.
PMP 197 is in civvies.

Swinging a leg over SHX 123.

PMP 195 may have started.

PMP 197 needs a good kick.

PMP 195 and SHX 123 head for the Palace.
Another Wren, at right, waits for them.

Passing Buckingham Palace.

Around the Victoria Memorial.

...and around it again.

Rider of PMP 194 has donned an overcoat.
Perhaps this photo was taken a different day.

Royal Enfield's new limited edition Despatch motorcycles its line of clothing inspired by military dispatch riders highlight the brand's connection to the services — and, of course, Royal Enfield's birth in India as the choice of the Indian military.