I am sorry to hear of the loss of your father.

Whilst several travel insurance policies do allow policyholders to screen for pre-existing medical conditions, many policies offered through Moneysupermarket do not have this facility and Flexicover.net seems to be one of these. It looks as if the Flexicover policy excludes any claims that are directly or indirectly related to any pre-existing medical condition.

Although I am not in the medical profession it is generally thought blood pressure is related to the cardiovascular and circulatory systems and uncontrolled blood pressure can lead to an increased risk of heart attack. The premiums on Moneysupermarket are calculated to reflect an Insured Person with no increased risk factors and it is for this reason that the Moneysupermarket warranty specifically warns policyholders that cover for any pre-existing medical conditions will not be available to both themselves and any person on whom the trip plans would depend.

http://www.moneysupermarket.com/travelinsurance/medicalhistory.asp

If you feel that you answered the medical warranty to the best of your knowledge at the time, then it may be worth contacting Flexicover through the complaints process in the wording and ask them to reconsider the claim.

Hope this helps