As a UK Ltd company is it legally expected that an IT company might bet the companies money and then claim the losses as an expense against that tax year?
Assuming the shareholders agree and that there is enough money in the company to pay creditors, there doesn't seem to be anything preventing it. It doesn't seem to be a disallowable expense.
That being said, I would suggest that trying to lose money gambling to claim as an expense is not a sensible course of action. Firstly, although likely, there is no certainty you will actually lose it, in which case it would defeat your objective. Secondly HMRC will not view it favourably and you would be at high risk of being flagged for a tax investigation, which can be time-consuming and costly (especially if they manage to find any anomalies).
If you want to reduce profits for tax purposes, talk to an accountant (or ask a new question). There may be additional expenses or reliefs you can legitimately claim (including the cost of the account's advice). They may also be able to help you with tax efficient strategies to disburse profits.
If you still have profits left over you for some reason want to "throw away" the safest and easiest way would be to make a donation to a registered charity. You can offset it against tax, you won't get it back and it will be legitimate in the eyes of HMRC.
If however the gambling was not authorised, i.e. someone had misappropriated company funds, then as with any other misuse of funds it would be a criminal offence that should be reported to the police. The loss can be offset against corporation tax, but would need to be done against the year the loss was discovered.
From a comment to another answer:
But actually its possible that somebody in the company spent a lot of money through the company on gambling, which while not causing a "problem", would be far simpler if we could claim it as a lose for the money that was lost.
This sounds dangerously close to embezzlement and or fraud (if that's not what you meant, please clarify in the question). If that were to be the case, how to deal with that would probably best be addressed in a different question (and probably not here, since it may no longer be within the bounds of Personal Finance).
However, if this is a case of – shall we say — "misused" funds, and you just want to "write it off" as a loss against profits, then doing so would seem to be allowed. The advice on "Tax relief on fraud" from accountingWEB suggests that such activity can be written-off as "money stolen" or "employee theft" – but keep all supporting documentation in case HMRC ask questions.