Ten people have been treated for suspected heat-related conditions on the first day of Wimbledon.

The Met Office said temperatures rose to 22C on Monday afternoon, far lower than the scorching conditions that hit London on Saturday.

At 3pm a spokeswoman for St John Ambulance said: "So far today St John volunteers have treated five people who are believed to have a heat-related condition. For example, this may be having a headache or feeling faint."

By 5pm that figure had risen to 10, another spokeswoman confirmed.

Earlier in the day there were reports of a ball boy collapsing during a first round match on Court 11.

Photos published online showed the boy being supported by Wimbledon officials.

A spokeswoman for the All England Club said: "It wasn't heat related and he is fine. He was not on court afterwards."

A spectator on Court 12 needed treatment earlier on Monday, but this was not heat related, the spokeswoman added.

Met Office forecaster Mark Wilson said conditions at Wimbledon had been "dry, with some sunshine".

"There's more sunshine to come over the next couple of days so that's good news," Mr Wilson said.

The temperature on Tuesday is expected to reach 22C, rising to 23C on Wednesday and 25C on Thursday and Friday.

The conditions are far cooler than the hottest Wimbledon day, on July 1 2015, when the mercury rose to 35.7C.

Wimbledon's heat rule, which allows 10-minute breaks in the middle of matches when the "heat stress index" reaches 30.1C, has been rolled out to all singles events this year.

Previously the rule only applied to the women's competition.

The good weather means the new retractable roof over No 1 Court may not be used.

Speaking to reporters on Monday, All England Club chief executive Richard Lewis said: "I've already been asked today about the fact that it may not be used because the weather forecast is good, very happy with that.

"If that's what the insurance premium costs, that's what it costs.

"But actually, we may of course use it for finishing matches under the roof if the light goes, so it's not unlikely actually the roof will be used.

"I will be surprised if it isn't used."