Lighting London's BT Tower

Architect: Eric Bedford
Lighting Design: Rufus Leonard, Tony Rimmer (Imagination)

Built in 1964, BT Tower was London’s tallest structure until 1990. A focal point of central London at 191 meters, the tower is instantly identifiable by its prominent BT signs that surround the building’s crown and are illuminated at night.

As part of a 20-month introduction of BT’s new “connected world” globe logo, London creative agency Rufus Leonard was asked to design a new lighting scheme, and design and events company Imagination developed and implemented the project.

Because of their specialist knowledge of exterior color-changing systems, A.C. Lighting’s UK Special Projects division was approached by Imagination’s architectural lighting design team to supply the lighting and control solution for the building’s new logo. A.C. Lighting supplied and programmed Martin Architectural fixtures for the new illuminated design. The challenge was to create a 360° representation of the logo using programmed color-changing sequences to reflect the logo’s complex globe shape and seven separate colors. The logo also needed to be integrated with the building’s existing BT signage.

Dynamic color changing is an important element of the image makeover. Imagination’s lighting designer, Tony Rimmer, commented, “The brief was to replicate the new ‘connected world’ logo. The old logo was being replaced with a new color-changing globe. Instead of having an actual graphic image we decided to replicate this by using color changing lights around the base of the new signage.”

Exterior 200
A.C. project manager Ceri Barraclough worked with Imagination’s lighting design team to devise a short list of potential lighting fixtures for testing in an on-site shoot-out. Of the three fixtures tested, Martin’s Exterior 200 was found to offer the best overall performance. Tony explains, “We did a shoot out between three different manufacturers and Martin produced the best light fitting and best color matching palette to the BT logo. The Martin Exterior 200 had the best optics and gave us the best coverage of the overall signage.”

Interior plc installed the new lighting system, which included extending the existing BT lightbox fascias to create a seamless 360° front projection panel, and removing the old “piper” logo from the lightbox signs. Some 48 IP65 rated Martin Exterior 200 CMY luminaires were then attached to the outside of the building and inverted all the way around the tower’s new signage and graphic panel to provide a seamless front projected, wall-washing beam of light.

Tony comments, “The fixtures were positioned at the bottom of the signage using custom brackets, 360 degrees all the way around with about a one degree elevation from vertical so it’s a very sharp incline, almost vertical. The fixtures are approximately two and a half meters from the base of the new signage, which measures about 4-6 meters high.”

Control and sequencing
The lighting sequence is triggered one hour after sunset and goes off one hour before sunrise. To operate the 48 fixtures required a control system with DMX capability, an astronomical clock and the ability to easily switch between various pre-programmed lighting sequences for special events. A.C.’s Projects division used their knowledge of architectural lighting controllers to specify an ETC Unison system and Chroma-Q™ Magic Box DMX distribution solutions. A.C. was also responsible for the installation and full programming of the system.

The main sequence involved dividing the fixtures into seven groups of light scenes, with each scene equating to a different color in the logo at any point in time. By fading the scene colors in and out while simultaneously rotating the groups in a set order, it gives the impression of the globe seamlessly rotating around the building’s crown.

Tony concludes, “The installation occurred in February of this year and the Martin fixtures have held up fine - there’s been no problems with them whatsoever. We are extremely pleased with the technical support and assistance received from A.C. Despite the difficult project conditions presented by working at such a height and the wind constraints, they developed our brief into a workable solution that ensured the lighting designs were executed without a hitch.”