It was her cue to explain that she is not rude or lazy, but is unable to walk or stand. She quotes the incident to show how people still expect barristers to be drawn from the ranks of the physically able.
The phrase "survival of the fittest" might have been coined for barristers. They are self-employed, and thrive or starve by their reputations. If successful, they need enormous stamina to cope with the workload. Small wonder that few of them are disabled. Yet Johnson, born with spina bifida, is a highly successful barrister in the criminal field.
Applications for pupillages show that other disabled people are determined to follow her lead. Not all will succeed.
Adrian Berrill-Cox, 33, who has muscular atrophy and uses a "minder" and an electric wheelchair to get around, now works as a regulatory lawyer for the Bank of England. He completed a criminal pupillage after he was called to the Bar in 1986, but did not obtain a tenancy. He warns: "The Bar is intensely competitive. Connections, intelligence, hard work and luck are all required.
"A physical disability is at best a handicap, and at worst the last straw. Using rubbish to build ramps outside the High Court, bumping up and down stairs, robing in lavatories, getting stuck in goods lifts and collecting parking tickets are not everyone's idea of fun.
"Nonetheless, if a disabled person is determined to try for the Bar, they should and will. Despite initial discouragement, fellow barristers will do all they can to help, and even clients can be very nice. I recall one murderer falling over himself to rearrange the furniture in the cells, and lighting my cigarettes all through a conference. Given the improvements to court buildings, and the possibly more enlightened attitudes of solicitors and clerks, I would try again, but for the financial risks."
One of the forces for change is the bar's Disability Panel, set up in 1992 by Recorder Gary Flather QC after he developed multiple sclerosis. The panel, the requirements of the Disability Act and changing attitudes are all helping to improve the prospects of disabled people.
Flather said: "Shortly after I took silk in '84 I developed multiple sclerosis and was forced to take sit-down jobs, such as working as a committee chairman. I move around in a wheelchair, and have bladder problems and problems with my hands. "I can take notes, but it takes time and it's difficult to turn pages. As a result, my memory has improved greatly. The Bar has no safety nets. If you fall ill it is catastrophic, because earning ability is affected if it is known that you have an impairment. For me, it was a very lonely business.
"The panel helps people with illness of all kinds - strokes, epilepsy, blindness, deafness, diabetes, depression and alcoholism. We try to match the person with someone with a similar disability. I am helping someone with MS. We also help disabled students. We don't want an elitist, physically fit profession. It should reflect society."
Many barristers with developing disabilities keep quiet. Others, with pre-existing disabilities, worry about life at the Bar being too tough. At one stage Gary Flather tried to conceal his MS, fearing he would lose work.
He added: "In spite of my fears, solicitors never turned a hair. Even clients joined in the spirit of the thing. On one occasion, having conducted a long cross-examination in the Chancery Division, I felt my knees lock. I whispered my dilemma to the client, sitting behind me. I said I would just have to fall back onto Counsel's Bench, and could he catch me? To which he replied, `If you don't mind I shall catch your head first, because that is the part I am paying for.'"
Zoe Johnson insists that being in a wheelchair can sometimes be advantageous when addressing a jury or talking to clients.
"Some clients think, `God, she must be good to have got to be a barrister.' In fact, I followed the same career path as my contemporaries.
"Crime is the most difficult area, because you are always dashing around. I drive everywhere and despite a battle with Westminster City Council they refuse to give me a disabled badge, because neither my chambers nor my home is in the area. So I pay quite a lot of money in parking tickets.
"I am lucky to be in a good set of chambers, doing some high-profile cases and getting instructions from top solicitors. Most buildings in the Inner Temple are hopeless - no lifts, and little staircases. New buildings must be properly designed for the disabled. People use the buildings as an excuse, but once someone can move around, that excuse is eradicated."
Help for disabled students is patchy but there are signs of a change in attitude. The Inner Temple, for example, gives disability grants for reading aids, special furniture, computers and other aids with the aim of creating a level playing-field for the disabled and the able-bodied.
A spokesman for the Court Service, which looks after 423 court buildings in England and Wales, said that a quarter of them are more than 100 years old, and 20 per cent are listed. Even though wheelchair ramps and lifts have been widely installed, access to a number of courtrooms is still possible only if court staff manhandle the disabled person up and down stairs.
The Court Service now plans to revise the design standards for new buildings, and a survey by architectural consultants has been proposed. Although most courts have rooms which have been adapted for disabled people, early notice to use them is often required, which is useless for disabled junior barristers who get cases at short notice.
Courtrooms also present problems for disabled judges, who may need help to mount the steps leading to their raised bench.
Gary Flather said: "Public access is a nonsense. We need to raise the profile of the disabled. In one County Court in West London the loo in the judge's chamber is too narrow for my wheelchair. I had to ask the usher to help me walk the few paces.
"I depend on the kindness and understanding of court staff. At Slough County Court, where I often sit, access for the disabled is very bad, but the staff are so kind, and make me so comfortable, that I go there despite the problems."Reuse content