But Walker saw the funny side, and soon cleared up the matter by Tweeting "Queuing... I said queuing. Well spotted by @james_seber this morning."
Thousands have been outside the Wimbledon grounds since Sunday, aiming to get their hands on one of around 6,000 daily ground passes.
It comes as security measures have been improved at the event in the wake of recent terror attacks.
Concrete barriers and robust metal gates were installed to stop vehicles ploughing into fans queuing for tickets.
Superintendent Jo Edwards, head of the security operation, said: "We take into account the threat level in UK and we take into account the atrocities that have taken place in the UK since March.
"The public will see a significant number of police officers and security staff visible in plain clothes or in uniform at different times of the day and night across the fortnight.
"That is designed to be really reassuring to visitors to the club."
She said there was no specific intelligence to suggest an attack was planned.